diff options
Diffstat (limited to 'third_party/heimdal/doc/layman.asc')
| -rw-r--r-- | third_party/heimdal/doc/layman.asc | 1855 |
1 files changed, 1855 insertions, 0 deletions
diff --git a/third_party/heimdal/doc/layman.asc b/third_party/heimdal/doc/layman.asc new file mode 100644 index 0000000..d4fbe64 --- /dev/null +++ b/third_party/heimdal/doc/layman.asc @@ -0,0 +1,1855 @@ +A Layman's Guide to a Subset of ASN.1, BER, and DER + +An RSA Laboratories Technical Note +Burton S. Kaliski Jr. +Revised November 1, 1993 + + +Supersedes June 3, 1991 version, which was also published as +NIST/OSI Implementors' Workshop document SEC-SIG-91-17. +PKCS documents are available by electronic mail to +<pkcs@rsa.com>. + +Copyright (C) 1991-1993 RSA Laboratories, a division of RSA +Data Security, Inc. License to copy this document is granted +provided that it is identified as "RSA Data Security, Inc. +Public-Key Cryptography Standards (PKCS)" in all material +mentioning or referencing this document. +003-903015-110-000-000 + + +Abstract. This note gives a layman's introduction to a +subset of OSI's Abstract Syntax Notation One (ASN.1), Basic +Encoding Rules (BER), and Distinguished Encoding Rules +(DER). The particular purpose of this note is to provide +background material sufficient for understanding and +implementing the PKCS family of standards. + + +1. Introduction + +It is a generally accepted design principle that abstraction +is a key to managing software development. With abstraction, +a designer can specify a part of a system without concern +for how the part is actually implemented or represented. +Such a practice leaves the implementation open; it +simplifies the specification; and it makes it possible to +state "axioms" about the part that can be proved when the +part is implemented, and assumed when the part is employed +in another, higher-level part. Abstraction is the hallmark +of most modern software specifications. + +One of the most complex systems today, and one that also +involves a great deal of abstraction, is Open Systems +Interconnection (OSI, described in X.200). OSI is an +internationally standardized architecture that governs the +interconnection of computers from the physical layer up to +the user application layer. Objects at higher layers are +defined abstractly and intended to be implemented with +objects at lower layers. For instance, a service at one +layer may require transfer of certain abstract objects +between computers; a lower layer may provide transfer +services for strings of ones and zeroes, using encoding +rules to transform the abstract objects into such strings. +OSI is called an open system because it supports many +different implementations of the services at each layer. + +OSI's method of specifying abstract objects is called ASN.1 +(Abstract Syntax Notation One, defined in X.208), and one +set of rules for representing such objects as strings of +ones and zeros is called the BER (Basic Encoding Rules, +defined in X.209). ASN.1 is a flexible notation that allows +one to define a variety data types, from simple types such +as integers and bit strings to structured types such as sets +and sequences, as well as complex types defined in terms of +others. BER describes how to represent or encode values of +each ASN.1 type as a string of eight-bit octets. There is +generally more than one way to BER-encode a given value. +Another set of rules, called the Distinguished Encoding +Rules (DER), which is a subset of BER, gives a unique +encoding to each ASN.1 value. + +The purpose of this note is to describe a subset of ASN.1, +BER and DER sufficient to understand and implement one OSI- +based application, RSA Data Security, Inc.'s Public-Key +Cryptography Standards. The features described include an +overview of ASN.1, BER, and DER and an abridged list of +ASN.1 types and their BER and DER encodings. Sections 2-4 +give an overview of ASN.1, BER, and DER, in that order. +Section 5 lists some ASN.1 types, giving their notation, +specific encoding rules, examples, and comments about their +application to PKCS. Section 6 concludes with an example, +X.500 distinguished names. + +Advanced features of ASN.1, such as macros, are not +described in this note, as they are not needed to implement +PKCS. For information on the other features, and for more +detail generally, the reader is referred to CCITT +Recommendations X.208 and X.209, which define ASN.1 and BER. + +Terminology and notation. In this note, an octet is an eight- +bit unsigned integer. Bit 8 of the octet is the most +significant and bit 1 is the least significant. + +The following meta-syntax is used for in describing ASN.1 +notation: + + BIT monospace denotes literal characters in the type + and value notation; in examples, it generally + denotes an octet value in hexadecimal + + n1 bold italics denotes a variable + + [] bold square brackets indicate that a term is + optional + + {} bold braces group related terms + + | bold vertical bar delimits alternatives with a + group + + ... bold ellipsis indicates repeated occurrences + + = bold equals sign expresses terms as subterms + + +2. Abstract Syntax Notation One + +Abstract Syntax Notation One, abbreviated ASN.1, is a +notation for describing abstract types and values. + +In ASN.1, a type is a set of values. For some types, there +are a finite number of values, and for other types there are +an infinite number. A value of a given ASN.1 type is an +element of the type's set. ASN.1 has four kinds of type: +simple types, which are "atomic" and have no components; +structured types, which have components; tagged types, which +are derived from other types; and other types, which include +the CHOICE type and the ANY type. Types and values can be +given names with the ASN.1 assignment operator (::=) , and +those names can be used in defining other types and values. + +Every ASN.1 type other than CHOICE and ANY has a tag, which +consists of a class and a nonnegative tag number. ASN.1 +types are abstractly the same if and only if their tag +numbers are the same. In other words, the name of an ASN.1 +type does not affect its abstract meaning, only the tag +does. There are four classes of tag: + + Universal, for types whose meaning is the same in all + applications; these types are only defined in + X.208. + + Application, for types whose meaning is specific to an + application, such as X.500 directory services; + types in two different applications may have the + same application-specific tag and different + meanings. + + Private, for types whose meaning is specific to a given + enterprise. + + Context-specific, for types whose meaning is specific + to a given structured type; context-specific tags + are used to distinguish between component types + with the same underlying tag within the context of + a given structured type, and component types in + two different structured types may have the same + tag and different meanings. + +The types with universal tags are defined in X.208, which +also gives the types' universal tag numbers. Types with +other tags are defined in many places, and are always +obtained by implicit or explicit tagging (see Section 2.3). +Table 1 lists some ASN.1 types and their universal-class +tags. + + Type Tag number Tag number + (decimal) (hexadecimal) + INTEGER 2 02 + BIT STRING 3 03 + OCTET STRING 4 04 + NULL 5 05 + OBJECT IDENTIFIER 6 06 + SEQUENCE and SEQUENCE OF 16 10 + SET and SET OF 17 11 + PrintableString 19 13 + T61String 20 14 + IA5String 22 16 + UTCTime 23 17 + + Table 1. Some types and their universal-class tags. + +ASN.1 types and values are expressed in a flexible, +programming-language-like notation, with the following +special rules: + + o Layout is not significant; multiple spaces and + line breaks can be considered as a single space. + + o Comments are delimited by pairs of hyphens (--), + or a pair of hyphens and a line break. + + o Identifiers (names of values and fields) and type + references (names of types) consist of upper- and + lower-case letters, digits, hyphens, and spaces; + identifiers begin with lower-case letters; type + references begin with upper-case letters. + +The following four subsections give an overview of simple +types, structured types, implicitly and explicitly tagged +types, and other types. Section 5 describes specific types +in more detail. + + +2.1 Simple types + +Simple types are those not consisting of components; they +are the "atomic" types. ASN.1 defines several; the types +that are relevant to the PKCS standards are the following: + + BIT STRING, an arbitrary string of bits (ones and + zeroes). + + IA5String, an arbitrary string of IA5 (ASCII) + characters. + + INTEGER, an arbitrary integer. + + NULL, a null value. + + OBJECT IDENTIFIER, an object identifier, which is a + sequence of integer components that identify an + object such as an algorithm or attribute type. + + OCTET STRING, an arbitrary string of octets (eight-bit + values). + + PrintableString, an arbitrary string of printable + characters. + + T61String, an arbitrary string of T.61 (eight-bit) + characters. + + UTCTime, a "coordinated universal time" or Greenwich + Mean Time (GMT) value. + +Simple types fall into two categories: string types and non- +string types. BIT STRING, IA5String, OCTET STRING, +PrintableString, T61String, and UTCTime are string types. + +String types can be viewed, for the purposes of encoding, as +consisting of components, where the components are +substrings. This view allows one to encode a value whose +length is not known in advance (e.g., an octet string value +input from a file stream) with a constructed, indefinite- +length encoding (see Section 3). + +The string types can be given size constraints limiting the +length of values. + + +2.2 Structured types + +Structured types are those consisting of components. ASN.1 +defines four, all of which are relevant to the PKCS +standards: + + SEQUENCE, an ordered collection of one or more types. + + SEQUENCE OF, an ordered collection of zero or more + occurrences of a given type. + + SET, an unordered collection of one or more types. + + SET OF, an unordered collection of zero or more + occurrences of a given type. + +The structured types can have optional components, possibly +with default values. + + +2.3 Implicitly and explicitly tagged types + +Tagging is useful to distinguish types within an +application; it is also commonly used to distinguish +component types within a structured type. For instance, +optional components of a SET or SEQUENCE type are typically +given distinct context-specific tags to avoid ambiguity. + +There are two ways to tag a type: implicitly and explicitly. + +Implicitly tagged types are derived from other types by +changing the tag of the underlying type. Implicit tagging is +denoted by the ASN.1 keywords [class number] IMPLICIT (see +Section 5.1). + +Explicitly tagged types are derived from other types by +adding an outer tag to the underlying type. In effect, +explicitly tagged types are structured types consisting of +one component, the underlying type. Explicit tagging is +denoted by the ASN.1 keywords [class number] EXPLICIT (see +Section 5.2). + +The keyword [class number] alone is the same as explicit +tagging, except when the "module" in which the ASN.1 type is +defined has implicit tagging by default. ("Modules" are +among the advanced features not described in this note.) + +For purposes of encoding, an implicitly tagged type is +considered the same as the underlying type, except that the +tag is different. An explicitly tagged type is considered +like a structured type with one component, the underlying +type. Implicit tags result in shorter encodings, but +explicit tags may be necessary to avoid ambiguity if the tag +of the underlying type is indeterminate (e.g., the +underlying type is CHOICE or ANY). + + +2.4 Other types + +Other types in ASN.1 include the CHOICE and ANY types. The +CHOICE type denotes a union of one or more alternatives; the +ANY type denotes an arbitrary value of an arbitrary type, +where the arbitrary type is possibly defined in the +registration of an object identifier or integer value. + + +3. Basic Encoding Rules + +The Basic Encoding Rules for ASN.1, abbreviated BER, give +one or more ways to represent any ASN.1 value as an octet +string. (There are certainly other ways to represent ASN.1 +values, but BER is the standard for interchanging such +values in OSI.) + +There are three methods to encode an ASN.1 value under BER, +the choice of which depends on the type of value and whether +the length of the value is known. The three methods are +primitive, definite-length encoding; constructed, definite- +length encoding; and constructed, indefinite-length +encoding. Simple non-string types employ the primitive, +definite-length method; structured types employ either of +the constructed methods; and simple string types employ any +of the methods, depending on whether the length of the value +is known. Types derived by implicit tagging employ the +method of the underlying type and types derived by explicit +tagging employ the constructed methods. + +In each method, the BER encoding has three or four parts: + + Identifier octets. These identify the class and tag + number of the ASN.1 value, and indicate whether + the method is primitive or constructed. + + Length octets. For the definite-length methods, these + give the number of contents octets. For the + constructed, indefinite-length method, these + indicate that the length is indefinite. + + Contents octets. For the primitive, definite-length + method, these give a concrete representation of + the value. For the constructed methods, these + give the concatenation of the BER encodings of the + components of the value. + + End-of-contents octets. For the constructed, indefinite- + length method, these denote the end of the + contents. For the other methods, these are absent. + +The three methods of encoding are described in the following +sections. + + +3.1 Primitive, definite-length method + +This method applies to simple types and types derived from +simple types by implicit tagging. It requires that the +length of the value be known in advance. The parts of the +BER encoding are as follows: + +Identifier octets. There are two forms: low tag number (for +tag numbers between 0 and 30) and high tag number (for tag +numbers 31 and greater). + + Low-tag-number form. One octet. Bits 8 and 7 specify + the class (see Table 2), bit 6 has value "0," + indicating that the encoding is primitive, and + bits 5-1 give the tag number. + + Class Bit Bit + 8 7 + universal 0 0 + application 0 1 + context-specific 1 0 + private 1 1 + + Table 2. Class encoding in identifier octets. + + High-tag-number form. Two or more octets. First octet + is as in low-tag-number form, except that bits 5-1 + all have value "1." Second and following octets + give the tag number, base 128, most significant + digit first, with as few digits as possible, and + with the bit 8 of each octet except the last set + to "1." + +Length octets. There are two forms: short (for lengths +between 0 and 127), and long definite (for lengths between 0 +and 21008-1). + + Short form. One octet. Bit 8 has value "0" and bits 7-1 + give the length. + + Long form. Two to 127 octets. Bit 8 of first octet has + value "1" and bits 7-1 give the number of + additional length octets. Second and following + octets give the length, base 256, most significant + digit first. + +Contents octets. These give a concrete representation of the +value (or the value of the underlying type, if the type is +derived by implicit tagging). Details for particular types +are given in Section 5. + + +3.2 Constructed, definite-length method + +This method applies to simple string types, structured +types, types derived simple string types and structured +types by implicit tagging, and types derived from anything +by explicit tagging. It requires that the length of the +value be known in advance. The parts of the BER encoding are +as follows: + +Identifier octets. As described in Section 3.1, except that +bit 6 has value "1," indicating that the encoding is +constructed. + +Length octets. As described in Section 3.1. + +Contents octets. The concatenation of the BER encodings of +the components of the value: + + o For simple string types and types derived from + them by implicit tagging, the concatenation of the + BER encodings of consecutive substrings of the + value (underlying value for implicit tagging). + + o For structured types and types derived from them + by implicit tagging, the concatenation of the BER + encodings of components of the value (underlying + value for implicit tagging). + + o For types derived from anything by explicit + tagging, the BER encoding of the underlying value. + +Details for particular types are given in Section 5. + + +3.3 Constructed, indefinite-length method + +This method applies to simple string types, structured +types, types derived simple string types and structured +types by implicit tagging, and types derived from anything +by explicit tagging. It does not require that the length of +the value be known in advance. The parts of the BER encoding +are as follows: + +Identifier octets. As described in Section 3.2. + +Length octets. One octet, 80. + +Contents octets. As described in Section 3.2. + +End-of-contents octets. Two octets, 00 00. + +Since the end-of-contents octets appear where an ordinary +BER encoding might be expected (e.g., in the contents octets +of a sequence value), the 00 and 00 appear as identifier and +length octets, respectively. Thus the end-of-contents octets +is really the primitive, definite-length encoding of a value +with universal class, tag number 0, and length 0. + + +4. Distinguished Encoding Rules + +The Distinguished Encoding Rules for ASN.1, abbreviated DER, +are a subset of BER, and give exactly one way to represent +any ASN.1 value as an octet string. DER is intended for +applications in which a unique octet string encoding is +needed, as is the case when a digital signature is computed +on an ASN.1 value. DER is defined in Section 8.7 of X.509. + +DER adds the following restrictions to the rules given in +Section 3: + + 1. When the length is between 0 and 127, the short + form of length must be used + + 2. When the length is 128 or greater, the long form + of length must be used, and the length must be + encoded in the minimum number of octets. + + 3. For simple string types and implicitly tagged + types derived from simple string types, the + primitive, definite-length method must be + employed. + + 4. For structured types, implicitly tagged types + derived from structured types, and explicitly + tagged types derived from anything, the + constructed, definite-length method must be + employed. + +Other restrictions are defined for particular types (such as +BIT STRING, SEQUENCE, SET, and SET OF), and can be found in +Section 5. + + +5. Notation and encodings for some types + +This section gives the notation for some ASN.1 types and +describes how to encode values of those types under both BER +and DER. + +The types described are those presented in Section 2. They +are listed alphabetically here. + +Each description includes ASN.1 notation, BER encoding, and +DER encoding. The focus of the encodings is primarily on the +contents octets; the tag and length octets follow Sections 3 +and 4. The descriptions also explain where each type is used +in PKCS and related standards. ASN.1 notation is generally +only for types, although for the type OBJECT IDENTIFIER, +value notation is given as well. + + +5.1 Implicitly tagged types + +An implicitly tagged type is a type derived from another +type by changing the tag of the underlying type. + +Implicit tagging is used for optional SEQUENCE components +with underlying type other than ANY throughout PKCS, and for +the extendedCertificate alternative of PKCS #7's +ExtendedCertificateOrCertificate type. + +ASN.1 notation: + +[[class] number] IMPLICIT Type + +class = UNIVERSAL | APPLICATION | PRIVATE + +where Type is a type, class is an optional class name, and +number is the tag number within the class, a nonnegative +integer. + +In ASN.1 "modules" whose default tagging method is implicit +tagging, the notation [[class] number] Type is also +acceptable, and the keyword IMPLICIT is implied. (See +Section 2.3.) For definitions stated outside a module, the +explicit inclusion of the keyword IMPLICIT is preferable to +prevent ambiguity. + +If the class name is absent, then the tag is context- +specific. Context-specific tags can only appear in a +component of a structured or CHOICE type. + +Example: PKCS #8's PrivateKeyInfo type has an optional +attributes component with an implicit, context-specific tag: + +PrivateKeyInfo ::= SEQUENCE { + version Version, + privateKeyAlgorithm PrivateKeyAlgorithmIdentifier, + privateKey PrivateKey, + attributes [0] IMPLICIT Attributes OPTIONAL } + +Here the underlying type is Attributes, the class is absent +(i.e., context-specific), and the tag number within the +class is 0. + +BER encoding. Primitive or constructed, depending on the +underlying type. Contents octets are as for the BER encoding +of the underlying value. + +Example: The BER encoding of the attributes component of a +PrivateKeyInfo value is as follows: + + o the identifier octets are 80 if the underlying + Attributes value has a primitive BER encoding and + a0 if the underlying Attributes value has a + constructed BER encoding + + o the length and contents octets are the same as the + length and contents octets of the BER encoding of + the underlying Attributes value + +DER encoding. Primitive or constructed, depending on the +underlying type. Contents octets are as for the DER encoding +of the underlying value. + + +5.2 Explicitly tagged types + +Explicit tagging denotes a type derived from another type by +adding an outer tag to the underlying type. + +Explicit tagging is used for optional SEQUENCE components +with underlying type ANY throughout PKCS, and for the +version component of X.509's Certificate type. + +ASN.1 notation: + +[[class] number] EXPLICIT Type + +class = UNIVERSAL | APPLICATION | PRIVATE + +where Type is a type, class is an optional class name, and +number is the tag number within the class, a nonnegative +integer. + +If the class name is absent, then the tag is context- +specific. Context-specific tags can only appear in a +component of a SEQUENCE, SET or CHOICE type. + +In ASN.1 "modules" whose default tagging method is explicit +tagging, the notation [[class] number] Type is also +acceptable, and the keyword EXPLICIT is implied. (See +Section 2.3.) For definitions stated outside a module, the +explicit inclusion of the keyword EXPLICIT is preferable to +prevent ambiguity. + +Example 1: PKCS #7's ContentInfo type has an optional +content component with an explicit, context-specific tag: + +ContentInfo ::= SEQUENCE { + contentType ContentType, + content + [0] EXPLICIT ANY DEFINED BY contentType OPTIONAL } + +Here the underlying type is ANY DEFINED BY contentType, the +class is absent (i.e., context-specific), and the tag number +within the class is 0. + +Example 2: X.509's Certificate type has a version component +with an explicit, context-specific tag, where the EXPLICIT +keyword is omitted: + +Certificate ::= ... + version [0] Version DEFAULT v1988, +... + +The tag is explicit because the default tagging method for +the ASN.1 "module" in X.509 that defines the Certificate +type is explicit tagging. + +BER encoding. Constructed. Contents octets are the BER +encoding of the underlying value. + +Example: the BER encoding of the content component of a +ContentInfo value is as follows: + + o identifier octets are a0 + + o length octets represent the length of the BER + encoding of the underlying ANY DEFINED BY + contentType value + + o contents octets are the BER encoding of the + underlying ANY DEFINED BY contentType value + +DER encoding. Constructed. Contents octets are the DER +encoding of the underlying value. + + +5.3 ANY + +The ANY type denotes an arbitrary value of an arbitrary +type, where the arbitrary type is possibly defined in the +registration of an object identifier or associated with an +integer index. + +The ANY type is used for content of a particular content +type in PKCS #7's ContentInfo type, for parameters of a +particular algorithm in X.509's AlgorithmIdentifier type, +and for attribute values in X.501's Attribute and +AttributeValueAssertion types. The Attribute type is used by +PKCS #6, #7, #8, #9 and #10, and the AttributeValueAssertion +type is used in X.501 distinguished names. + +ASN.1 notation: + +ANY [DEFINED BY identifier] + +where identifier is an optional identifier. + +In the ANY form, the actual type is indeterminate. + +The ANY DEFINED BY identifier form can only appear in a +component of a SEQUENCE or SET type for which identifier +identifies some other component, and that other component +has type INTEGER or OBJECT IDENTIFIER (or a type derived +from either of those by tagging). In that form, the actual +type is determined by the value of the other component, +either in the registration of the object identifier value, +or in a table of integer values. + +Example: X.509's AlgorithmIdentifier type has a component of +type ANY: + +AlgorithmIdentifier ::= SEQUENCE { + algorithm OBJECT IDENTIFIER, + parameters ANY DEFINED BY algorithm OPTIONAL } + +Here the actual type of the parameter component depends on +the value of the algorithm component. The actual type would +be defined in the registration of object identifier values +for the algorithm component. + +BER encoding. Same as the BER encoding of the actual value. + +Example: The BER encoding of the value of the parameter +component is the BER encoding of the value of the actual +type as defined in the registration of object identifier +values for the algorithm component. + +DER encoding. Same as the DER encoding of the actual value. + + +5.4 BIT STRING + +The BIT STRING type denotes an arbitrary string of bits +(ones and zeroes). A BIT STRING value can have any length, +including zero. This type is a string type. + +The BIT STRING type is used for digital signatures on +extended certificates in PKCS #6's ExtendedCertificate type, +for digital signatures on certificates in X.509's +Certificate type, and for public keys in certificates in +X.509's SubjectPublicKeyInfo type. + +ASN.1 notation: + +BIT STRING + +Example: X.509's SubjectPublicKeyInfo type has a component +of type BIT STRING: + +SubjectPublicKeyInfo ::= SEQUENCE { + algorithm AlgorithmIdentifier, + publicKey BIT STRING } + +BER encoding. Primitive or constructed. In a primitive +encoding, the first contents octet gives the number of bits +by which the length of the bit string is less than the next +multiple of eight (this is called the "number of unused +bits"). The second and following contents octets give the +value of the bit string, converted to an octet string. The +conversion process is as follows: + + 1. The bit string is padded after the last bit with + zero to seven bits of any value to make the length + of the bit string a multiple of eight. If the + length of the bit string is a multiple of eight + already, no padding is done. + + 2. The padded bit string is divided into octets. The + first eight bits of the padded bit string become + the first octet, bit 8 to bit 1, and so on through + the last eight bits of the padded bit string. + +In a constructed encoding, the contents octets give the +concatenation of the BER encodings of consecutive substrings +of the bit string, where each substring except the last has +a length that is a multiple of eight bits. + +Example: The BER encoding of the BIT STRING value +"011011100101110111" can be any of the following, among +others, depending on the choice of padding bits, the form of +length octets, and whether the encoding is primitive or +constructed: + +03 04 06 6e 5d c0 DER encoding + +03 04 06 6e 5d e0 padded with "100000" + +03 81 04 06 6e 5d c0 long form of length octets + +23 09 constructed encoding: "0110111001011101" + "11" + 03 03 00 6e 5d + 03 02 06 c0 + +DER encoding. Primitive. The contents octects are as for a +primitive BER encoding, except that the bit string is padded +with zero-valued bits. + +Example: The DER encoding of the BIT STRING value +"011011100101110111" is + +03 04 06 6e 5d c0 + + +5.5 CHOICE + +The CHOICE type denotes a union of one or more alternatives. + +The CHOICE type is used to represent the union of an +extended certificate and an X.509 certificate in PKCS #7's +ExtendedCertificateOrCertificate type. + +ASN.1 notation: + +CHOICE { + [identifier1] Type1, + ..., + [identifiern] Typen } + +where identifier1 , ..., identifiern are optional, distinct +identifiers for the alternatives, and Type1, ..., Typen are +the types of the alternatives. The identifiers are primarily +for documentation; they do not affect values of the type or +their encodings in any way. + +The types must have distinct tags. This requirement is +typically satisfied with explicit or implicit tagging on +some of the alternatives. + +Example: PKCS #7's ExtendedCertificateOrCertificate type is +a CHOICE type: + +ExtendedCertificateOrCertificate ::= CHOICE { + certificate Certificate, -- X.509 + extendedCertificate [0] IMPLICIT ExtendedCertificate +} + +Here the identifiers for the alternatives are certificate +and extendedCertificate, and the types of the alternatives +are Certificate and [0] IMPLICIT ExtendedCertificate. + +BER encoding. Same as the BER encoding of the chosen +alternative. The fact that the alternatives have distinct +tags makes it possible to distinguish between their BER +encodings. + +Example: The identifier octets for the BER encoding are 30 +if the chosen alternative is certificate, and a0 if the +chosen alternative is extendedCertificate. + +DER encoding. Same as the DER encoding of the chosen +alternative. + + +5.6 IA5String + +The IA5String type denotes an arbtrary string of IA5 +characters. IA5 stands for International Alphabet 5, which +is the same as ASCII. The character set includes non- +printing control characters. An IA5String value can have any +length, including zero. This type is a string type. + +The IA5String type is used in PKCS #9's electronic-mail +address, unstructured-name, and unstructured-address +attributes. + +ASN.1 notation: + +IA5String + +BER encoding. Primitive or constructed. In a primitive +encoding, the contents octets give the characters in the IA5 +string, encoded in ASCII. In a constructed encoding, the +contents octets give the concatenation of the BER encodings +of consecutive substrings of the IA5 string. + +Example: The BER encoding of the IA5String value +"test1@rsa.com" can be any of the following, among others, +depending on the form of length octets and whether the +encoding is primitive or constructed: + +16 0d 74 65 73 74 31 40 72 73 61 2e 63 6f 6d DER encoding + +16 81 0d long form of length octets + 74 65 73 74 31 40 72 73 61 2e 63 6f 6d + +36 13 constructed encoding: "test1" + "@" + "rsa.com" + 16 05 74 65 73 74 31 + 16 01 40 + 16 07 72 73 61 2e 63 6f 6d + +DER encoding. Primitive. Contents octets are as for a +primitive BER encoding. + +Example: The DER encoding of the IA5String value +"test1@rsa.com" is + +16 0d 74 65 73 74 31 40 72 73 61 2e 63 6f 6d + + +5.7 INTEGER + +The INTEGER type denotes an arbitrary integer. INTEGER +values can be positive, negative, or zero, and can have any +magnitude. + +The INTEGER type is used for version numbers throughout +PKCS, cryptographic values such as modulus, exponent, and +primes in PKCS #1's RSAPublicKey and RSAPrivateKey types and +PKCS #3's DHParameter type, a message-digest iteration count +in PKCS #5's PBEParameter type, and version numbers and +serial numbers in X.509's Certificate type. + +ASN.1 notation: + +INTEGER [{ identifier1(value1) ... identifiern(valuen) }] + +where identifier1, ..., identifiern are optional distinct +identifiers and value1, ..., valuen are optional integer +values. The identifiers, when present, are associated with +values of the type. + +Example: X.509's Version type is an INTEGER type with +identified values: + +Version ::= INTEGER { v1988(0) } + +The identifier v1988 is associated with the value 0. X.509's +Certificate type uses the identifier v1988 to give a default +value of 0 for the version component: + +Certificate ::= ... + version Version DEFAULT v1988, +... + +BER encoding. Primitive. Contents octets give the value of +the integer, base 256, in two's complement form, most +significant digit first, with the minimum number of octets. +The value 0 is encoded as a single 00 octet. + +Some example BER encodings (which also happen to be DER +encodings) are given in Table 3. + + Integer BER encoding + value + 0 02 01 00 + 127 02 01 7F + 128 02 02 00 80 + 256 02 02 01 00 + -128 02 01 80 + -129 02 02 FF 7F + + Table 3. Example BER encodings of INTEGER values. + +DER encoding. Primitive. Contents octets are as for a +primitive BER encoding. + + +5.8 NULL + +The NULL type denotes a null value. + +The NULL type is used for algorithm parameters in several +places in PKCS. + +ASN.1 notation: + +NULL + +BER encoding. Primitive. Contents octets are empty. + +Example: The BER encoding of a NULL value can be either of +the following, as well as others, depending on the form of +the length octets: + +05 00 + +05 81 00 + +DER encoding. Primitive. Contents octets are empty; the DER +encoding of a NULL value is always 05 00. + + +5.9 OBJECT IDENTIFIER + +The OBJECT IDENTIFIER type denotes an object identifier, a +sequence of integer components that identifies an object +such as an algorithm, an attribute type, or perhaps a +registration authority that defines other object +identifiers. An OBJECT IDENTIFIER value can have any number +of components, and components can generally have any +nonnegative value. This type is a non-string type. + +OBJECT IDENTIFIER values are given meanings by registration +authorities. Each registration authority is responsible for +all sequences of components beginning with a given sequence. +A registration authority typically delegates responsibility +for subsets of the sequences in its domain to other +registration authorities, or for particular types of object. +There are always at least two components. + +The OBJECT IDENTIFIER type is used to identify content in +PKCS #7's ContentInfo type, to identify algorithms in +X.509's AlgorithmIdentifier type, and to identify attributes +in X.501's Attribute and AttributeValueAssertion types. The +Attribute type is used by PKCS #6, #7, #8, #9, and #10, and +the AttributeValueAssertion type is used in X.501 +distinguished names. OBJECT IDENTIFIER values are defined +throughout PKCS. + +ASN.1 notation: + +OBJECT IDENTIFIER + +The ASN.1 notation for values of the OBJECT IDENTIFIER type +is + +{ [identifier] component1 ... componentn } + +componenti = identifieri | identifieri (valuei) | valuei + +where identifier, identifier1, ..., identifiern are +identifiers, and value1, ..., valuen are optional integer +values. + +The form without identifier is the "complete" value with all +its components; the form with identifier abbreviates the +beginning components with another object identifier value. +The identifiers identifier1, ..., identifiern are intended +primarily for documentation, but they must correspond to the +integer value when both are present. These identifiers can +appear without integer values only if they are among a small +set of identifiers defined in X.208. + +Example: The following values both refer to the object +identifier assigned to RSA Data Security, Inc.: + +{ iso(1) member-body(2) 840 113549 } +{ 1 2 840 113549 } + +(In this example, which gives ASN.1 value notation, the +object identifier values are decimal, not hexadecimal.) +Table 4 gives some other object identifier values and their +meanings. + + Object identifier value Meaning + { 1 2 } ISO member bodies + { 1 2 840 } US (ANSI) + { 1 2 840 113549 } RSA Data Security, Inc. + { 1 2 840 113549 1 } RSA Data Security, Inc. PKCS + { 2 5 } directory services (X.500) + { 2 5 8 } directory services-algorithms + + Table 4. Some object identifier values and their meanings. + +BER encoding. Primitive. Contents octets are as follows, +where value1, ..., valuen denote the integer values of the +components in the complete object identifier: + + 1. The first octet has value 40 * value1 + value2. + (This is unambiguous, since value1 is limited to + values 0, 1, and 2; value2 is limited to the range + 0 to 39 when value1 is 0 or 1; and, according to + X.208, n is always at least 2.) + + 2. The following octets, if any, encode value3, ..., + valuen. Each value is encoded base 128, most + significant digit first, with as few digits as + possible, and the most significant bit of each + octet except the last in the value's encoding set + to "1." + +Example: The first octet of the BER encoding of RSA Data +Security, Inc.'s object identifier is 40 * 1 + 2 = 42 = +2a16. The encoding of 840 = 6 * 128 + 4816 is 86 48 and the +encoding of 113549 = 6 * 1282 + 7716 * 128 + d16 is 86 f7 +0d. This leads to the following BER encoding: + +06 06 2a 86 48 86 f7 0d + +DER encoding. Primitive. Contents octets are as for a +primitive BER encoding. + + +5.10 OCTET STRING + +The OCTET STRING type denotes an arbitrary string of octets +(eight-bit values). An OCTET STRING value can have any +length, including zero. This type is a string type. + +The OCTET STRING type is used for salt values in PKCS #5's +PBEParameter type, for message digests, encrypted message +digests, and encrypted content in PKCS #7, and for private +keys and encrypted private keys in PKCS #8. + +ASN.1 notation: + +OCTET STRING [SIZE ({size | size1..size2})] + +where size, size1, and size2 are optional size constraints. +In the OCTET STRING SIZE (size) form, the octet string must +have size octets. In the OCTET STRING SIZE (size1..size2) +form, the octet string must have between size1 and size2 +octets. In the OCTET STRING form, the octet string can have +any size. + +Example: PKCS #5's PBEParameter type has a component of type +OCTET STRING: + +PBEParameter ::= SEQUENCE { + salt OCTET STRING SIZE(8), + iterationCount INTEGER } + +Here the size of the salt component is always eight octets. + +BER encoding. Primitive or constructed. In a primitive +encoding, the contents octets give the value of the octet +string, first octet to last octet. In a constructed +encoding, the contents octets give the concatenation of the +BER encodings of substrings of the OCTET STRING value. + +Example: The BER encoding of the OCTET STRING value 01 23 45 +67 89 ab cd ef can be any of the following, among others, +depending on the form of length octets and whether the +encoding is primitive or constructed: + +04 08 01 23 45 67 89 ab cd ef DER encoding + +04 81 08 01 23 45 67 89 ab cd ef long form of length octets + +24 0c constructed encoding: 01 ... 67 + 89 ... ef + 04 04 01 23 45 67 + 04 04 89 ab cd ef + +DER encoding. Primitive. Contents octets are as for a +primitive BER encoding. + +Example: The BER encoding of the OCTET STRING value 01 23 45 +67 89 ab cd ef is + +04 08 01 23 45 67 89 ab cd ef + + +5.11 PrintableString + +The PrintableString type denotes an arbitrary string of +printable characters from the following character set: + + A, B, ..., Z + a, b, ..., z + 0, 1, ..., 9 + (space) ' ( ) + , - . / : = ? + +This type is a string type. + +The PrintableString type is used in PKCS #9's challenge- +password and unstructuerd-address attributes, and in several +X.521 distinguished names attributes. + +ASN.1 notation: + +PrintableString + +BER encoding. Primitive or constructed. In a primitive +encoding, the contents octets give the characters in the +printable string, encoded in ASCII. In a constructed +encoding, the contents octets give the concatenation of the +BER encodings of consecutive substrings of the string. + +Example: The BER encoding of the PrintableString value "Test +User 1" can be any of the following, among others, depending +on the form of length octets and whether the encoding is +primitive or constructed: + +13 0b 54 65 73 74 20 55 73 65 72 20 31 DER encoding + +13 81 0b long form of length octets + 54 65 73 74 20 55 73 65 72 20 31 + +33 0f constructed encoding: "Test " + "User 1" + 13 05 54 65 73 74 20 + 13 06 55 73 65 72 20 31 + +DER encoding. Primitive. Contents octets are as for a +primitive BER encoding. + +Example: The DER encoding of the PrintableString value "Test +User 1" is + +13 0b 54 65 73 74 20 55 73 65 72 20 31 + + +5.12 SEQUENCE + +The SEQUENCE type denotes an ordered collection of one or +more types. + +The SEQUENCE type is used throughout PKCS and related +standards. + +ASN.1 notation: + +SEQUENCE { + [identifier1] Type1 [{OPTIONAL | DEFAULT value1}], + ..., + [identifiern] Typen [{OPTIONAL | DEFAULT valuen}]} + +where identifier1 , ..., identifiern are optional, distinct +identifiers for the components, Type1, ..., Typen are the +types of the components, and value1, ..., valuen are optional +default values for the components. The identifiers are +primarily for documentation; they do not affect values of +the type or their encodings in any way. + +The OPTIONAL qualifier indicates that the value of a +component is optional and need not be present in the +sequence. The DEFAULT qualifier also indicates that the +value of a component is optional, and assigns a default +value to the component when the component is absent. + +The types of any consecutive series of components with the +OPTIONAL or DEFAULT qualifier, as well as of any component +immediately following that series, must have distinct tags. +This requirement is typically satisfied with explicit or +implicit tagging on some of the components. + +Example: X.509's Validity type is a SEQUENCE type with two +components: + +Validity ::= SEQUENCE { + start UTCTime, + end UTCTime } + +Here the identifiers for the components are start and end, +and the types of the components are both UTCTime. + +BER encoding. Constructed. Contents octets are the +concatenation of the BER encodings of the values of the +components of the sequence, in order of definition, with the +following rules for components with the OPTIONAL and DEFAULT +qualifiers: + + o if the value of a component with the OPTIONAL or + DEFAULT qualifier is absent from the sequence, + then the encoding of that component is not + included in the contents octets + + o if the value of a component with the DEFAULT + qualifier is the default value, then the encoding + of that component may or may not be included in + the contents octets + +DER encoding. Constructed. Contents octets are the same as +the BER encoding, except that if the value of a component +with the DEFAULT qualifier is the default value, the +encoding of that component is not included in the contents +octets. + + +5.13 SEQUENCE OF + +The SEQUENCE OF type denotes an ordered collection of zero +or more occurrences of a given type. + +The SEQUENCE OF type is used in X.501 distinguished names. + +ASN.1 notation: + +SEQUENCE OF Type + +where Type is a type. + +Example: X.501's RDNSequence type consists of zero or more +occurences of the RelativeDistinguishedName type, most +significant occurrence first: + +RDNSequence ::= SEQUENCE OF RelativeDistinguishedName + +BER encoding. Constructed. Contents octets are the +concatenation of the BER encodings of the values of the +occurrences in the collection, in order of occurence. + +DER encoding. Constructed. Contents octets are the +concatenation of the DER encodings of the values of the +occurrences in the collection, in order of occurence. + + +5.14 SET + +The SET type denotes an unordered collection of one or more +types. + +The SET type is not used in PKCS. + +ASN.1 notation: + +SET { + [identifier1] Type1 [{OPTIONAL | DEFAULT value1}], + ..., + [identifiern] Typen [{OPTIONAL | DEFAULT valuen}]} + +where identifier1, ..., identifiern are optional, distinct +identifiers for the components, Type1, ..., Typen are the +types of the components, and value1, ..., valuen are +optional default values for the components. The identifiers +are primarily for documentation; they do not affect values +of the type or their encodings in any way. + +The OPTIONAL qualifier indicates that the value of a +component is optional and need not be present in the set. +The DEFAULT qualifier also indicates that the value of a +component is optional, and assigns a default value to the +component when the component is absent. + +The types must have distinct tags. This requirement is +typically satisfied with explicit or implicit tagging on +some of the components. + +BER encoding. Constructed. Contents octets are the +concatenation of the BER encodings of the values of the +components of the set, in any order, with the following +rules for components with the OPTIONAL and DEFAULT +qualifiers: + + o if the value of a component with the OPTIONAL or + DEFAULT qualifier is absent from the set, then the + encoding of that component is not included in the + contents octets + + o if the value of a component with the DEFAULT + qualifier is the default value, then the encoding + of that component may or may not be included in + the contents octets + +DER encoding. Constructed. Contents octets are the same as +for the BER encoding, except that: + + 1. If the value of a component with the DEFAULT + qualifier is the default value, the encoding of + that component is not included. + + 2. There is an order to the components, namely + ascending order by tag. + + +5.15 SET OF + +The SET OF type denotes an unordered collection of zero or +more occurrences of a given type. + +The SET OF type is used for sets of attributes in PKCS #6, +#7, #8, #9 and #10, for sets of message-digest algorithm +identifiers, signer information, and recipient information +in PKCS #7, and in X.501 distinguished names. + +ASN.1 notation: + +SET OF Type + +where Type is a type. + +Example: X.501's RelativeDistinguishedName type consists of +zero or more occurrences of the AttributeValueAssertion +type, where the order is unimportant: + +RelativeDistinguishedName ::= + SET OF AttributeValueAssertion + +BER encoding. Constructed. Contents octets are the +concatenation of the BER encodings of the values of the +occurrences in the collection, in any order. + +DER encoding. Constructed. Contents octets are the same as +for the BER encoding, except that there is an order, namely +ascending lexicographic order of BER encoding. Lexicographic +comparison of two different BER encodings is done as +follows: Logically pad the shorter BER encoding after the +last octet with dummy octets that are smaller in value than +any normal octet. Scan the BER encodings from left to right +until a difference is found. The smaller-valued BER encoding +is the one with the smaller-valued octet at the point of +difference. + + +5.16 T61String + +The T61String type denotes an arbtrary string of T.61 +characters. T.61 is an eight-bit extension to the ASCII +character set. Special "escape" sequences specify the +interpretation of subsequent character values as, for +example, Japanese; the initial interpretation is Latin. The +character set includes non-printing control characters. The +T61String type allows only the Latin and Japanese character +interepretations, and implementors' agreements for directory +names exclude control characters [NIST92]. A T61String value +can have any length, including zero. This type is a string +type. + +The T61String type is used in PKCS #9's unstructured-address +and challenge-password attributes, and in several X.521 +attributes. + +ASN.1 notation: + +T61String + +BER encoding. Primitive or constructed. In a primitive +encoding, the contents octets give the characters in the +T.61 string, encoded in ASCII. In a constructed encoding, +the contents octets give the concatenation of the BER +encodings of consecutive substrings of the T.61 string. + +Example: The BER encoding of the T61String value "cl'es +publiques" (French for "public keys") can be any of the +following, among others, depending on the form of length +octets and whether the encoding is primitive or constructed: + +14 0f DER encoding + 63 6c c2 65 73 20 70 75 62 6c 69 71 75 65 73 + +14 81 0f long form of length octets + 63 6c c2 65 73 20 70 75 62 6c 69 71 75 65 73 + +34 15 constructed encoding: "cl'es" + " " + "publiques" + 14 05 63 6c c2 65 73 + 14 01 20 + 14 09 70 75 62 6c 69 71 75 65 73 + +The eight-bit character c2 is a T.61 prefix that adds an +acute accent (') to the next character. + +DER encoding. Primitive. Contents octets are as for a +primitive BER encoding. + +Example: The DER encoding of the T61String value "cl'es +publiques" is + +14 0f 63 6c c2 65 73 20 70 75 62 6c 69 71 75 65 73 + + +5.17 UTCTime + +The UTCTime type denotes a "coordinated universal time" or +Greenwich Mean Time (GMT) value. A UTCTime value includes +the local time precise to either minutes or seconds, and an +offset from GMT in hours and minutes. It takes any of the +following forms: + +YYMMDDhhmmZ +YYMMDDhhmm+hh'mm' +YYMMDDhhmm-hh'mm' +YYMMDDhhmmssZ +YYMMDDhhmmss+hh'mm' +YYMMDDhhmmss-hh'mm' + +where: + + YY is the least significant two digits of the year + + MM is the month (01 to 12) + + DD is the day (01 to 31) + + hh is the hour (00 to 23) + + mm are the minutes (00 to 59) + + ss are the seconds (00 to 59) + + Z indicates that local time is GMT, + indicates that + local time is later than GMT, and - indicates that + local time is earlier than GMT + + hh' is the absolute value of the offset from GMT in + hours + + mm' is the absolute value of the offset from GMT in + minutes + +This type is a string type. + +The UTCTime type is used for signing times in PKCS #9's +signing-time attribute and for certificate validity periods +in X.509's Validity type. + +ASN.1 notation: + +UTCTime + +BER encoding. Primitive or constructed. In a primitive +encoding, the contents octets give the characters in the +string, encoded in ASCII. In a constructed encoding, the +contents octets give the concatenation of the BER encodings +of consecutive substrings of the string. (The constructed +encoding is not particularly interesting, since UTCTime +values are so short, but the constructed encoding is +permitted.) + +Example: The time this sentence was originally written was +4:45:40 p.m. Pacific Daylight Time on May 6, 1991, which can +be represented with either of the following UTCTime values, +among others: + +"910506164540-0700" + +"910506234540Z" + +These values have the following BER encodings, among others: + +17 0d 39 31 30 35 30 36 32 33 34 35 34 30 5a + +17 11 39 31 30 35 30 36 31 36 34 35 34 30 2D 30 37 30 + 30 + +DER encoding. Primitive. Contents octets are as for a +primitive BER encoding. + + +6. An example + +This section gives an example of ASN.1 notation and DER +encoding: the X.501 type Name. + + +6.1 Abstract notation + +This section gives the ASN.1 notation for the X.501 type +Name. + +Name ::= CHOICE { + RDNSequence } + +RDNSequence ::= SEQUENCE OF RelativeDistinguishedName + +RelativeDistinguishedName ::= + SET OF AttributeValueAssertion + +AttributeValueAssertion ::= SEQUENCE { + AttributeType, + AttributeValue } + +AttributeType ::= OBJECT IDENTIFIER + +AttributeValue ::= ANY + +The Name type identifies an object in an X.500 directory. +Name is a CHOICE type consisting of one alternative: +RDNSequence. (Future revisions of X.500 may have other +alternatives.) + +The RDNSequence type gives a path through an X.500 directory +tree starting at the root. RDNSequence is a SEQUENCE OF type +consisting of zero or more occurences of +RelativeDistinguishedName. + +The RelativeDistinguishedName type gives a unique name to an +object relative to the object superior to it in the +directory tree. RelativeDistinguishedName is a SET OF type +consisting of zero or more occurrences of +AttributeValueAssertion. + +The AttributeValueAssertion type assigns a value to some +attribute of a relative distinguished name, such as country +name or common name. AttributeValueAssertion is a SEQUENCE +type consisting of two components, an AttributeType type and +an AttributeValue type. + +The AttributeType type identifies an attribute by object +identifier. The AttributeValue type gives an arbitrary +attribute value. The actual type of the attribute value is +determined by the attribute type. + + +6.2 DER encoding + +This section gives an example of a DER encoding of a value +of type Name, working from the bottom up. + +The name is that of the Test User 1 from the PKCS examples +[Kal93]. The name is represented by the following path: + + (root) + | + countryName = "US" + | + organizationName = "Example Organization" + | + commonName = "Test User 1" + +Each level corresponds to one RelativeDistinguishedName +value, each of which happens for this name to consist of one +AttributeValueAssertion value. The AttributeType value is +before the equals sign, and the AttributeValue value (a +printable string for the given attribute types) is after the +equals sign. + +The countryName, organizationName, and commonUnitName are +attribute types defined in X.520 as: + +attributeType OBJECT IDENTIFIER ::= + { joint-iso-ccitt(2) ds(5) 4 } + +countryName OBJECT IDENTIFIER ::= { attributeType 6 } +organizationName OBJECT IDENTIFIER ::= + { attributeType 10 } +commonUnitName OBJECT IDENTIFIER ::= + { attributeType 3 } + + +6.2.1 AttributeType + +The three AttributeType values are OCTET STRING values, so +their DER encoding follows the primitive, definite-length +method: + +06 03 55 04 06 countryName + +06 03 55 04 0a organizationName + +06 03 55 04 03 commonName + +The identifier octets follow the low-tag form, since the tag +is 6 for OBJECT IDENTIFIER. Bits 8 and 7 have value "0," +indicating universal class, and bit 6 has value "0," +indicating that the encoding is primitive. The length octets +follow the short form. The contents octets are the +concatenation of three octet strings derived from +subidentifiers (in decimal): 40 * 2 + 5 = 85 = 5516; 4; and +6, 10, or 3. + + +6.2.2 AttributeValue + +The three AttributeValue values are PrintableString values, +so their encodings follow the primitive, definite-length +method: + +13 02 55 53 "US" + +13 14 "Example Organization" + 45 78 61 6d 70 6c 65 20 4f 72 67 61 6e 69 7a 61 + 74 69 6f 6e + +13 0b "Test User 1" + 54 65 73 74 20 55 73 65 72 20 31 + +The identifier octets follow the low-tag-number form, since +the tag for PrintableString, 19 (decimal), is between 0 and +30. Bits 8 and 7 have value "0" since PrintableString is in +the universal class. Bit 6 has value "0" since the encoding +is primitive. The length octets follow the short form, and +the contents octets are the ASCII representation of the +attribute value. + + +6.2.3 AttributeValueAssertion + +The three AttributeValueAssertion values are SEQUENCE +values, so their DER encodings follow the constructed, +definite-length method: + +30 09 countryName = "US" + 06 03 55 04 06 + 13 02 55 53 + +30 1b organizationName = "Example Organizaiton" + 06 03 55 04 0a + 13 14 ... 6f 6e + +30 12 commonName = "Test User 1" + 06 03 55 04 0b + 13 0b ... 20 31 + +The identifier octets follow the low-tag-number form, since +the tag for SEQUENCE, 16 (decimal), is between 0 and 30. +Bits 8 and 7 have value "0" since SEQUENCE is in the +universal class. Bit 6 has value "1" since the encoding is +constructed. The length octets follow the short form, and +the contents octets are the concatenation of the DER +encodings of the attributeType and attributeValue +components. + + +6.2.4 RelativeDistinguishedName + +The three RelativeDistinguishedName values are SET OF +values, so their DER encodings follow the constructed, +definite-length method: + +31 0b + 30 09 ... 55 53 + +31 1d + 30 1b ... 6f 6e + +31 14 + 30 12 ... 20 31 + +The identifier octets follow the low-tag-number form, since +the tag for SET OF, 17 (decimal), is between 0 and 30. Bits +8 and 7 have value "0" since SET OF is in the universal +class Bit 6 has value "1" since the encoding is constructed. +The lengths octets follow the short form, and the contents +octets are the DER encodings of the respective +AttributeValueAssertion values, since there is only one +value in each set. + + +6.2.5 RDNSequence + +The RDNSequence value is a SEQUENCE OF value, so its DER +encoding follows the constructed, definite-length method: + +30 42 + 31 0b ... 55 53 + 31 1d ... 6f 6e + 31 14 ... 20 31 + +The identifier octets follow the low-tag-number form, since +the tag for SEQUENCE OF, 16 (decimal), is between 0 and 30. +Bits 8 and 7 have value "0" since SEQUENCE OF is in the +universal class. Bit 6 has value "1" since the encoding is +constructed. The lengths octets follow the short form, and +the contents octets are the concatenation of the DER +encodings of the three RelativeDistinguishedName values, in +order of occurrence. + + +6.2.6 Name + +The Name value is a CHOICE value, so its DER encoding is the +same as that of the RDNSequence value: + +30 42 + 31 0b + 30 09 + 06 03 55 04 06 attributeType = countryName + 13 02 55 53 attributeValue = "US" + 31 1d + 30 1b + 06 03 55 04 0a attributeType = organizationName + 13 14 attributeValue = "Example Organization" + 45 78 61 6d 70 6c 65 20 4f 72 67 61 6e 69 7a 61 + 74 69 6f 6e + + 31 14 + 30 12 + 06 03 55 04 03 attributeType = commonName + 13 0b attributeValue = "Test User 1" + 54 65 73 74 20 55 73 65 72 20 31 + + +References + +PKCS #1 RSA Laboratories. PKCS #1: RSA Encryption + Standard. Version 1.5, November 1993. + +PKCS #3 RSA Laboratories. PKCS #3: Diffie-Hellman Key- + Agreement Standard. Version 1.4, November 1993. + +PKCS #5 RSA Laboratories. PKCS #5: Password-Based + Encryption Standard. Version 1.5, November 1993. + +PKCS #6 RSA Laboratories. PKCS #6: Extended-Certificate + Syntax Standard. Version 1.5, November 1993. + +PKCS #7 RSA Laboratories. PKCS #7: Cryptographic Message + Syntax Standard. Version 1.5, November 1993. + +PKCS #8 RSA Laboratories. PKCS #8: Private-Key Information + Syntax Standard. Version 1.2, November 1993. + +PKCS #9 RSA Laboratories. PKCS #9: Selected Attribute + Types. Version 1.1, November 1993. + +PKCS #10 RSA Laboratories. PKCS #10: Certification Request + Syntax Standard. Version 1.0, November 1993. + +X.200 CCITT. Recommendation X.200: Reference Model of + Open Systems Interconnection for CCITT + Applications. 1984. + +X.208 CCITT. Recommendation X.208: Specification of + Abstract Syntax Notation One (ASN.1). 1988. + +X.209 CCITT. Recommendation X.209: Specification of + Basic Encoding Rules for Abstract Syntax Notation + One (ASN.1). 1988. + +X.500 CCITT. Recommendation X.500: The + Directory--Overview of Concepts, Models and + Services. 1988. + +X.501 CCITT. Recommendation X.501: The Directory-- + Models. 1988. + +X.509 CCITT. Recommendation X.509: The Directory-- + Authentication Framework. 1988. + +X.520 CCITT. Recommendation X.520: The Directory-- + Selected Attribute Types. 1988. + +[Kal93] Burton S. Kaliski Jr. Some Examples of the PKCS + Standards. RSA Laboratories, November 1993. + +[NIST92] NIST. Special Publication 500-202: Stable + Implementation Agreements for Open Systems + Interconnection Protocols. Part 11 (Directory + Services Protocols). December 1992. + + +Revision history + + +June 3, 1991 version + +The June 3, 1991 version is part of the initial public +release of PKCS. It was published as NIST/OSI Implementors' +Workshop document SEC-SIG-91-17. + + +November 1, 1993 version + +The November 1, 1993 version incorporates several editorial +changes, including the addition of a revision history. It is +updated to be consistent with the following versions of the +PKCS documents: + + PKCS #1: RSA Encryption Standard. Version 1.5, November + 1993. + + PKCS #3: Diffie-Hellman Key-Agreement Standard. Version + 1.4, November 1993. + + PKCS #5: Password-Based Encryption Standard. Version + 1.5, November 1993. + + PKCS #6: Extended-Certificate Syntax Standard. Version + 1.5, November 1993. + + PKCS #7: Cryptographic Message Syntax Standard. Version + 1.5, November 1993. + + PKCS #8: Private-Key Information Syntax Standard. + Version 1.2, November 1993. + + PKCS #9: Selected Attribute Types. Version 1.1, + November 1993. + + PKCS #10: Certification Request Syntax Standard. + Version 1.0, November 1993. + +The following substantive changes were made: + + Section 5: Description of T61String type is added. + + Section 6: Names are changed, consistent with other + PKCS examples. + + +Author's address + +Burton S. Kaliski Jr., Ph.D. +Chief Scientist +RSA Laboratories (415) 595-7703 +100 Marine Parkway (415) 595-4126 (fax) +Redwood City, CA 94065 USA burt@rsa.com |