KEYRING-CRYPT(2) KEYRING-CRYPT(2)
NAME
keyring: aessetup, aescbc, dessetup, descbc, desecb,
ideasetup, ideacbc, ideaecb - data encryption
SYNOPSIS
include "keyring.m";
keyring := load Keyring Keyring->PATH;
Encrypt: con 0;
Decrypt: con 1;
AESbsize: con 16;
aessetup: fn(key: array of byte, ivec: array of byte): ref AESstate;
aescbc: fn(state: ref AESstate, buf: array of byte,
n: int, direction: int);
BFbsize: con 8;
blowfishsetup: fn(key: array of byte, ivec: array of byte): ref BFstate;
blowfishcbc: fn(state: ref BFstate, buf: array of byte,
n: int, direction: int);
DESbsize: con 8;
dessetup: fn(key: array of byte, ivec: array of byte): ref DESstate;
descbc: fn(state: ref DESstate, buf: array of byte,
n: int, direction: int);
desecb: fn(state: ref DESstate, buf: array of byte,
n: int, direction: int);
IDEAbsize: con 8;
ideasetup: fn(key: array of byte, ivec: array of byte): ref IDEAstate;
ideacbc: fn(state: ref IDEAstate, buf: array of byte,
n: int, direction: int);
ideaecb: fn(state: ref IDEAstate, buf: array of byte,
n: int, direction: int);
DESCRIPTION
These functions encrypt and decrypt blocks of data using
different encryption algorithms. The interfaces are
similar.
Each algorithm has an adt that holds the current state for a
given encryption. It is produced by the setup function for
the algorithm, algsetup, which is given a secret key and an
initialisation vector ivec. A sequence of blocks of data can
then be encrypted or decrypted by repeatedly calling algcbc
(for `cipher block chaining'), or algebc (the less secure
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KEYRING-CRYPT(2) KEYRING-CRYPT(2)
`electronic code book', if provided). On each call, buf
provides n bytes of the data to encrypt or decrypt. N must
be a multiple of the encryption block size ALGbsize. Excep-
tionally, aescbc allows n to be other than a multiple of
AESbsize in length, but then for successful decryption, the
decryptor must use the same sequence of buffer sizes as the
encryptor. Direction is the constant Encrypt or Decrypt as
required. State maintains the encryption state, initially
produced by the setup function, and updated as each buffer
is encrypted or decrypted.
The algorithms currently available are:
aes The Advanced Encryption Standard, AES (also known as
Rijndael). The key should be 16, 24 or 32 bytes long
(128, 192 or 256 bits). Ivec should be AESbsize bytes
of random data: random enough to be unlikely to be
reused but not cryptographically strongly unpre-
dictable.
blowfish
Bruce Schneier's symmetric block cipher. The key is
any length from 4 to 56 bytes. Ivec if non-nil is
BFbsize bytes of random data. For blowfishcbc, n must
be a multiple of BFbsize.
des The older Data Encryption Standard, DES. Key is 8
bytes (64 bits), containing a 56-bit key encoded into
64 bits where every eighth bit is parity. Ivec is
DESbsize bytes of random data.
idea The International Data Encryption Standard, IDEA™. The
key is 16 bytes long (128 bits). Ivec is IDEAbsize
bytes of random data.
SEE ALSO
keyring-intro(2), keyring-rc4(2), security-random(2)
IDEA was patented by Ascom-Tech AG (EP 0 482 154 B1,
US005214703), currently held by iT_SEC Systec Ltd. At time
of writing, there was no licence fee required for noncommer-
cial use but check the current licensing policy of iT_SEC
Systec Ltd, especially for commercial use.
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