The ecb_crypt and cbc_crypt functions implement the NBS DES (Data Encryption Standard). These routines are faster and more general purpose than crypt(3). They also are able to utilize DES hardware if it is available. The ecb_crypt function encrypts in ECB (Electronic Code Book) mode, which encrypts blocks of data independently. The cbc_crypt function encrypts in CBC (Cipher Block Chaining) mode, which chains together successive blocks. CBC mode protects against insertions, deletions and substitutions of blocks. Also, regularities in the clear text will not appear in the cipher text.
Here is how to use these routines. The first argument, key, is the 8-byte encryption key with parity. To set the keys parity, which for DES is in the low bit of each byte, use des_setparity. The second argument, data, contains the data to be encrypted or decrypted. The third argument, datalen, is the length in bytes of data, which must be a multiple of 8. The fourth argument, mode, is formed by OR ing together some things. For the encryption direction OR in either DES_ENCRYPT or DES_DECRYPT. For software versus hardware encryption, OR in either DES_HW or DES_SW. If DES_HW is specified, and there is no hardware, then the encryption is performed in software and the routine returns DESERR_NOHWDEVICE. For cbc_crypt, the ivec argument is the 8-byte initialization vector for the chaining. It is updated to the next initialization vector upon return.