Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 98 insertions, 0 deletions

diff --git a/comm/third_party/botan/doc/api_ref/fpe.rst b/comm/third_party/botan/doc/api_ref/fpe.rst
new file mode 100644
index 0000000000..9d77a40864
--- /dev/null
+++ b/comm/third_party/botan/doc/api_ref/fpe.rst
@@ -0,0 +1,98 @@
+Format Preserving Encryption
+========================================
+
+Format preserving encryption (FPE) refers to a set of techniques for
+encrypting data such that the ciphertext has the same format as the
+plaintext. For instance, you can use FPE to encrypt credit card
+numbers with valid checksums such that the ciphertext is also an
+credit card number with a valid checksum, or similarly for bank
+account numbers, US Social Security numbers, or even more general
+mappings like English words onto other English words.
+
+The scheme currently implemented in botan is called FE1, and described
+in the paper `Format Preserving Encryption
+<https://eprint.iacr.org/2009/251>`_ by Mihir Bellare, Thomas
+Ristenpart, Phillip Rogaway, and Till Stegers. FPE is an area of
+ongoing standardization and it is likely that other schemes will be
+included in the future.
+
+To encrypt an arbitrary value using FE1, you need to use a ranking
+method. Basically, the idea is to assign an integer to every value you
+might encrypt. For instance, a 16 digit credit card number consists of
+a 15 digit code plus a 1 digit checksum. So to encrypt a credit card
+number, you first remove the checksum, encrypt the 15 digit value
+modulo 10\ :sup:`15`, and then calculate what the checksum is for the
+new (ciphertext) number. Or, if you were encrypting words in a
+dictionary, you could rank the words by their lexicographical order,
+and choose the modulus to be the number of words in the dictionary.
+
+The interfaces for FE1 are defined in the header ``fpe_fe1.h``:
+
+.. versionadded:: 2.5.0
+
+.. cpp:class:: FPE_FE1
+
+   .. cpp:function:: FPE_FE1(const BigInt& n, size_t rounds = 5, \
+                             bool compat_mode = false,           \
+                             std::string mac_algo = "HMAC(SHA-256)")
+
+      Initialize an FPE operation to encrypt/decrypt integers less
+      than *n*. It is expected that *n* is trivially factorable into
+      small integers. Common usage would be n to be a power of 10.
+
+      Note that the default parameters to this constructor are
+      **incompatible** with the ``fe1_encrypt`` and ``fe1_decrypt``
+      function originally added in 1.9.17. For compatibility, use
+      3 rounds and set ``compat_mode`` to true.
+
+   .. cpp:function:: BigInt encrypt(const BigInt& x, const uint8_t tweak[], size_t tweak_len) const
+
+      Encrypts the value *x* modulo the value *n* using the *key* and *tweak*
+      specified. Returns an integer less than *n*. The *tweak* is a value that
+      does not need to be secret that parameterizes the encryption function. For
+      instance, if you were encrypting a database column with a single key, you
+      could use a per-row-unique integer index value as the tweak. The same
+      tweak value must be used during decryption.
+
+   .. cpp:function:: BigInt decrypt(const BigInt& x, const uint8_t tweak[], size_t tweak_len) const
+
+      Decrypts an FE1 ciphertext. The *tweak* must be the same as that provided
+      to the encryption function. Returns the plaintext integer.
+
+      Note that there is not any implicit authentication or checking of data in
+      FE1, so if you provide an incorrect key or tweak the result is simply a
+      random integer.
+
+   .. cpp:function:: BigInt encrypt(const BigInt& x, uint64_t tweak)
+
+      Convenience version of encrypt taking an integer tweak.
+
+   .. cpp:function:: BigInt decrypt(const BigInt& x, uint64_t tweak)
+
+      Convenience version of decrypt taking an integer tweak.
+
+There are two functions that handle the entire FE1 encrypt/decrypt operation.
+These are the original interface to FE1, first added in 1.9.17. However because
+they do the entire setup cost for each operation, they are significantly slower
+than the class-based API presented above.
+
+.. warning:: These functions are hardcoded to use 3 rounds, which may be
+             insufficient depending on the chosen modulus.
+
+.. cpp:function:: BigInt FPE::fe1_encrypt(const BigInt& n, const BigInt& X, \
+             const SymmetricKey& key, const std::vector<uint8_t>& tweak)
+
+    This creates an FPE_FE1 object, sets the key, and encrypts *X* using
+    the provided tweak.
+
+.. cpp:function:: BigInt FPE::fe1_decrypt(const BigInt& n, const BigInt& X, \
+             const SymmetricKey& key, const std::vector<uint8_t>& tweak)
+
+    This creates an FPE_FE1 object, sets the key, and decrypts *X* using
+    the provided tweak.
+
+This example encrypts a credit card number with a valid `Luhn checksum
+<https://en.wikipedia.org/wiki/Luhn_algorithm>`_ to another number with the same
+format, including a correct checksum.
+
+.. literalinclude:: ../../src/cli/cc_enc.cpp