pgcrypto encryption for specific columns The pgcrypto module provides cryptographic functions for PostgreSQL. This module is considered trusted, that is, it can be installed by non-superusers who have CREATE privilege on the current database. digest digest(data text, type text) returns bytea digest(data bytea, type text) returns bytea Computes a binary hash of the given data. type is the algorithm to use. Standard algorithms are md5, sha1, sha224, sha256, sha384 and sha512. If pgcrypto was built with OpenSSL, more algorithms are available, as detailed in . If you want the digest as a hexadecimal string, use encode() on the result. For example: CREATE OR REPLACE FUNCTION sha1(bytea) returns text AS $$ SELECT encode(digest($1, 'sha1'), 'hex') $$ LANGUAGE SQL STRICT IMMUTABLE; hmac hmac(data text, key text, type text) returns bytea hmac(data bytea, key bytea, type text) returns bytea Calculates hashed MAC for data with key key. type is the same as in digest(). This is similar to digest() but the hash can only be recalculated knowing the key. This prevents the scenario of someone altering data and also changing the hash to match. If the key is larger than the hash block size it will first be hashed and the result will be used as key. The functions crypt() and gen_salt() are specifically designed for hashing passwords. crypt() does the hashing and gen_salt() prepares algorithm parameters for it. The algorithms in crypt() differ from the usual MD5 or SHA1 hashing algorithms in the following respects: They are slow. As the amount of data is so small, this is the only way to make brute-forcing passwords hard. They use a random value, called the salt, so that users having the same password will have different encrypted passwords. This is also an additional defense against reversing the algorithm. They include the algorithm type in the result, so passwords hashed with different algorithms can co-exist. Some of them are adaptive — that means when computers get faster, you can tune the algorithm to be slower, without introducing incompatibility with existing passwords. lists the algorithms supported by the crypt() function. Algorithm Max Password Length Adaptive? Salt Bits Output Length Description bf 72 yes 128 60 Blowfish-based, variant 2a md5 unlimited no 48 34 MD5-based crypt xdes 8 yes 24 20 Extended DES des 8 no 12 13 Original UNIX crypt crypt crypt(password text, salt text) returns text Calculates a crypt(3)-style hash of password. When storing a new password, you need to use gen_salt() to generate a new salt value. To check a password, pass the stored hash value as salt, and test whether the result matches the stored value. Example of setting a new password: UPDATE ... SET pswhash = crypt('new password', gen_salt('md5')); Example of authentication: SELECT (pswhash = crypt('entered password', pswhash)) AS pswmatch FROM ... ; This returns true if the entered password is correct. gen_salt gen_salt(type text [, iter_count integer ]) returns text Generates a new random salt string for use in crypt(). The salt string also tells crypt() which algorithm to use. The type parameter specifies the hashing algorithm. The accepted types are: des, xdes, md5 and bf. The iter_count parameter lets the user specify the iteration count, for algorithms that have one. The higher the count, the more time it takes to hash the password and therefore the more time to break it. Although with too high a count the time to calculate a hash may be several years — which is somewhat impractical. If the iter_count parameter is omitted, the default iteration count is used. Allowed values for iter_count depend on the algorithm and are shown in . Algorithm Default Min Max xdes 725 1 16777215 bf 6 4 31 For xdes there is an additional limitation that the iteration count must be an odd number. To pick an appropriate iteration count, consider that the original DES crypt was designed to have the speed of 4 hashes per second on the hardware of that time. Slower than 4 hashes per second would probably dampen usability. Faster than 100 hashes per second is probably too fast. gives an overview of the relative slowness of different hashing algorithms. The table shows how much time it would take to try all combinations of characters in an 8-character password, assuming that the password contains either only lower case letters, or upper- and lower-case letters and numbers. In the crypt-bf entries, the number after a slash is the iter_count parameter of gen_salt. Algorithm Hashes/sec For [a-z] For [A-Za-z0-9] Duration relative to md5 hash crypt-bf/8 1792 4 years 3927 years 100k crypt-bf/7 3648 2 years 1929 years 50k crypt-bf/6 7168 1 year 982 years 25k crypt-bf/5 13504 188 days 521 years 12.5k crypt-md5 171584 15 days 41 years 1k crypt-des 23221568 157.5 minutes 108 days 7 sha1 37774272 90 minutes 68 days 4 md5 (hash) 150085504 22.5 minutes 17 days 1 Notes: The machine used is an Intel Mobile Core i3. crypt-des and crypt-md5 algorithm numbers are taken from John the Ripper v1.6.38 -test output. md5 hash numbers are from mdcrack 1.2. sha1 numbers are from lcrack-20031130-beta. crypt-bf numbers are taken using a simple program that loops over 1000 8-character passwords. That way I can show the speed with different numbers of iterations. For reference: john -test shows 13506 loops/sec for crypt-bf/5. (The very small difference in results is in accordance with the fact that the crypt-bf implementation in pgcrypto is the same one used in John the Ripper.) Note that try all combinations is not a realistic exercise. Usually password cracking is done with the help of dictionaries, which contain both regular words and various mutations of them. So, even somewhat word-like passwords could be cracked much faster than the above numbers suggest, while a 6-character non-word-like password may escape cracking. Or not. The functions here implement the encryption part of the OpenPGP (RFC 4880) standard. Supported are both symmetric-key and public-key encryption. An encrypted PGP message consists of 2 parts, or packets: Packet containing a session key — either symmetric-key or public-key encrypted. Packet containing data encrypted with the session key. When encrypting with a symmetric key (i.e., a password): The given password is hashed using a String2Key (S2K) algorithm. This is rather similar to crypt() algorithms — purposefully slow and with random salt — but it produces a full-length binary key. If a separate session key is requested, a new random key will be generated. Otherwise the S2K key will be used directly as the session key. If the S2K key is to be used directly, then only S2K settings will be put into the session key packet. Otherwise the session key will be encrypted with the S2K key and put into the session key packet. When encrypting with a public key: A new random session key is generated. It is encrypted using the public key and put into the session key packet. In either case the data to be encrypted is processed as follows: Optional data-manipulation: compression, conversion to UTF-8, and/or conversion of line-endings. The data is prefixed with a block of random bytes. This is equivalent to using a random IV. An SHA1 hash of the random prefix and data is appended. All this is encrypted with the session key and placed in the data packet. pgp_sym_encrypt pgp_sym_encrypt_bytea pgp_sym_encrypt(data text, psw text [, options text ]) returns bytea pgp_sym_encrypt_bytea(data bytea, psw text [, options text ]) returns bytea Encrypt data with a symmetric PGP key psw. The options parameter can contain option settings, as described below. pgp_sym_decrypt pgp_sym_decrypt_bytea pgp_sym_decrypt(msg bytea, psw text [, options text ]) returns text pgp_sym_decrypt_bytea(msg bytea, psw text [, options text ]) returns bytea Decrypt a symmetric-key-encrypted PGP message. Decrypting bytea data with pgp_sym_decrypt is disallowed. This is to avoid outputting invalid character data. Decrypting originally textual data with pgp_sym_decrypt_bytea is fine. The options parameter can contain option settings, as described below. pgp_pub_encrypt pgp_pub_encrypt_bytea pgp_pub_encrypt(data text, key bytea [, options text ]) returns bytea pgp_pub_encrypt_bytea(data bytea, key bytea [, options text ]) returns bytea Encrypt data with a public PGP key key. Giving this function a secret key will produce an error. The options parameter can contain option settings, as described below. pgp_pub_decrypt pgp_pub_decrypt_bytea pgp_pub_decrypt(msg bytea, key bytea [, psw text [, options text ]]) returns text pgp_pub_decrypt_bytea(msg bytea, key bytea [, psw text [, options text ]]) returns bytea Decrypt a public-key-encrypted message. key must be the secret key corresponding to the public key that was used to encrypt. If the secret key is password-protected, you must give the password in psw. If there is no password, but you want to specify options, you need to give an empty password. Decrypting bytea data with pgp_pub_decrypt is disallowed. This is to avoid outputting invalid character data. Decrypting originally textual data with pgp_pub_decrypt_bytea is fine. The options parameter can contain option settings, as described below. pgp_key_id pgp_key_id(bytea) returns text pgp_key_id extracts the key ID of a PGP public or secret key. Or it gives the key ID that was used for encrypting the data, if given an encrypted message. It can return 2 special key IDs: SYMKEY The message is encrypted with a symmetric key. ANYKEY The message is public-key encrypted, but the key ID has been removed. That means you will need to try all your secret keys on it to see which one decrypts it. pgcrypto itself does not produce such messages. Note that different keys may have the same ID. This is rare but a normal event. The client application should then try to decrypt with each one, to see which fits — like handling ANYKEY. armor dearmor armor(data bytea [ , keys text[], values text[] ]) returns text dearmor(data text) returns bytea These functions wrap/unwrap binary data into PGP ASCII-armor format, which is basically Base64 with CRC and additional formatting. If the keys and values arrays are specified, an armor header is added to the armored format for each key/value pair. Both arrays must be single-dimensional, and they must be of the same length. The keys and values cannot contain any non-ASCII characters. pgp_armor_headers pgp_armor_headers(data text, key out text, value out text) returns setof record pgp_armor_headers() extracts the armor headers from data. The return value is a set of rows with two columns, key and value. If the keys or values contain any non-ASCII characters, they are treated as UTF-8. Options are named to be similar to GnuPG. An option's value should be given after an equal sign; separate options from each other with commas. For example: pgp_sym_encrypt(data, psw, 'compress-algo=1, cipher-algo=aes256') All of the options except convert-crlf apply only to encrypt functions. Decrypt functions get the parameters from the PGP data. The most interesting options are probably compress-algo and unicode-mode. The rest should have reasonable defaults. Which cipher algorithm to use. Values: bf, aes128, aes192, aes256 (OpenSSL-only: 3des, cast5) Default: aes128 Applies to: pgp_sym_encrypt, pgp_pub_encrypt Which compression algorithm to use. Only available if PostgreSQL was built with zlib. Values: 0 - no compression 1 - ZIP compression 2 - ZLIB compression (= ZIP plus meta-data and block CRCs) Default: 0 Applies to: pgp_sym_encrypt, pgp_pub_encrypt How much to compress. Higher levels compress smaller but are slower. 0 disables compression. Values: 0, 1-9 Default: 6 Applies to: pgp_sym_encrypt, pgp_pub_encrypt Whether to convert \n into \r\n when encrypting and \r\n to \n when decrypting. RFC 4880 specifies that text data should be stored using \r\n line-feeds. Use this to get fully RFC-compliant behavior. Values: 0, 1 Default: 0 Applies to: pgp_sym_encrypt, pgp_pub_encrypt, pgp_sym_decrypt, pgp_pub_decrypt Do not protect data with SHA-1. The only good reason to use this option is to achieve compatibility with ancient PGP products, predating the addition of SHA-1 protected packets to RFC 4880. Recent gnupg.org and pgp.com software supports it fine. Values: 0, 1 Default: 0 Applies to: pgp_sym_encrypt, pgp_pub_encrypt Use separate session key. Public-key encryption always uses a separate session key; this option is for symmetric-key encryption, which by default uses the S2K key directly. Values: 0, 1 Default: 0 Applies to: pgp_sym_encrypt Which S2K algorithm to use. Values: 0 - Without salt. Dangerous! 1 - With salt but with fixed iteration count. 3 - Variable iteration count. Default: 3 Applies to: pgp_sym_encrypt The number of iterations of the S2K algorithm to use. It must be a value between 1024 and 65011712, inclusive. Default: A random value between 65536 and 253952 Applies to: pgp_sym_encrypt, only with s2k-mode=3 Which digest algorithm to use in S2K calculation. Values: md5, sha1 Default: sha1 Applies to: pgp_sym_encrypt Which cipher to use for encrypting separate session key. Values: bf, aes, aes128, aes192, aes256 Default: use cipher-algo Applies to: pgp_sym_encrypt Whether to convert textual data from database internal encoding to UTF-8 and back. If your database already is UTF-8, no conversion will be done, but the message will be tagged as UTF-8. Without this option it will not be. Values: 0, 1 Default: 0 Applies to: pgp_sym_encrypt, pgp_pub_encrypt To generate a new key: gpg --gen-key The preferred key type is DSA and Elgamal. For RSA encryption you must create either DSA or RSA sign-only key as master and then add an RSA encryption subkey with gpg --edit-key. To list keys: gpg --list-secret-keys To export a public key in ASCII-armor format: gpg -a --export KEYID > public.key To export a secret key in ASCII-armor format: gpg -a --export-secret-keys KEYID > secret.key You need to use dearmor() on these keys before giving them to the PGP functions. Or if you can handle binary data, you can drop -a from the command. For more details see man gpg, The GNU Privacy Handbook and other documentation on . No support for signing. That also means that it is not checked whether the encryption subkey belongs to the master key. No support for encryption key as master key. As such practice is generally discouraged, this should not be a problem. No support for several subkeys. This may seem like a problem, as this is common practice. On the other hand, you should not use your regular GPG/PGP keys with pgcrypto, but create new ones, as the usage scenario is rather different. These functions only run a cipher over data; they don't have any advanced features of PGP encryption. Therefore they have some major problems: They use user key directly as cipher key. They don't provide any integrity checking, to see if the encrypted data was modified. They expect that users manage all encryption parameters themselves, even IV. They don't handle text. So, with the introduction of PGP encryption, usage of raw encryption functions is discouraged. encrypt decrypt encrypt_iv decrypt_iv encrypt(data bytea, key bytea, type text) returns bytea decrypt(data bytea, key bytea, type text) returns bytea encrypt_iv(data bytea, key bytea, iv bytea, type text) returns bytea decrypt_iv(data bytea, key bytea, iv bytea, type text) returns bytea Encrypt/decrypt data using the cipher method specified by type. The syntax of the type string is: algorithm - mode /pad: padding where algorithm is one of: bf — Blowfish aes — AES (Rijndael-128, -192 or -256) and mode is one of: cbc — next block depends on previous (default) ecb — each block is encrypted separately (for testing only) and padding is one of: pkcs — data may be any length (default) none — data must be multiple of cipher block size So, for example, these are equivalent: encrypt(data, 'fooz', 'bf') encrypt(data, 'fooz', 'bf-cbc/pad:pkcs') In encrypt_iv and decrypt_iv, the iv parameter is the initial value for the CBC mode; it is ignored for ECB. It is clipped or padded with zeroes if not exactly block size. It defaults to all zeroes in the functions without this parameter. gen_random_bytes gen_random_bytes(count integer) returns bytea Returns count cryptographically strong random bytes. At most 1024 bytes can be extracted at a time. This is to avoid draining the randomness generator pool. gen_random_uuid gen_random_uuid() returns uuid Returns a version 4 (random) UUID. (Obsolete, this function is now also included in core PostgreSQL.) pgcrypto configures itself according to the findings of the main PostgreSQL configure script. The options that affect it are --with-zlib and --with-openssl. When compiled with zlib, PGP encryption functions are able to compress data before encrypting. When compiled with OpenSSL, there will be more algorithms available. Also public-key encryption functions will be faster as OpenSSL has more optimized BIGNUM functions. Functionality Built-in With OpenSSL MD5 yes yes SHA1 yes yes SHA224/256/384/512 yes yes Other digest algorithms no yes (Note 1) Blowfish yes yes AES yes yes DES/3DES/CAST5 no yes Raw encryption yes yes PGP Symmetric encryption yes yes PGP Public-Key encryption yes yes Notes: Any digest algorithm OpenSSL supports is automatically picked up. This is not possible with ciphers, which need to be supported explicitly. As is standard in SQL, all functions return NULL, if any of the arguments are NULL. This may create security risks on careless usage. All pgcrypto functions run inside the database server. That means that all the data and passwords move between pgcrypto and client applications in clear text. Thus you must: Connect locally or use SSL connections. Trust both system and database administrator. If you cannot, then better do crypto inside client application. The implementation does not resist side-channel attacks. For example, the time required for a pgcrypto decryption function to complete varies among ciphertexts of a given size. The GNU Privacy Handbook. Describes the crypt-blowfish algorithm. How to choose a good password. Interesting idea for picking passwords. Describes good and bad cryptography. OpenPGP message format. The MD5 Message-Digest Algorithm. HMAC: Keyed-Hashing for Message Authentication. Comparison of crypt-des, crypt-md5 and bcrypt algorithms. Description of Fortuna CSPRNG. Jean-Luc Cooke Fortuna-based /dev/random driver for Linux. Marko Kreen markokr@gmail.com pgcrypto uses code from the following sources: Algorithm Author Source origin DES crypt David Burren and others FreeBSD libcrypt MD5 crypt Poul-Henning Kamp FreeBSD libcrypt Blowfish crypt Solar Designer www.openwall.com Blowfish cipher Simon Tatham PuTTY Rijndael cipher Brian Gladman OpenBSD sys/crypto MD5 hash and SHA1 WIDE Project KAME kame/sys/crypto SHA256/384/512 Aaron D. Gifford OpenBSD sys/crypto BIGNUM math Michael J. Fromberger dartmouth.edu/~sting/sw/imath