= crypt: aessetup, aescbc, dessetup, descbc, desecb, ideasetup, ideacbc, ideaecb: data encryption     include "ipints.m";    include "crypt.m";    crypt := load Crypt Crypt->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); These functions encrypt and decrypt blocks of data using dif‐ferent encryption algorithms.  The interfaces are similar. Each  algorithm has an adt that holds the current state for agiven encryption.  It is produced by the setup  function  forthe  algorithm,  algsetup, which is given a secret key and aninitialisation vector ivec.  A sequence of blocks of data canthen  be  encrypted or decrypted by repeatedly calling algcbc(for `cipher block chaining'), or  algebc  (the  less  secure`electronic code book', if provided).  On each call, buf pro‐vides n bytes of the data to encrypt or decrypt.  N must be amultiple  of  the encryption block size ALGbsize.  Exception‐ally, aescbc allows n to be other than a multiple of AESbsizein  length, but then for successful decryption, the decryptormust 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  bythe  setup  function, and updated as each buffer is encryptedor 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  IDEAb‐       size bytes of random data. == see ALSOcrypt-intro(2), crypt-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.   Thepatent expired in 2012.