crypt(), setkey(), encrypt(), des_setkey(), des_cipher() - DES encryption
char * crypt (const char *key, const char *setting)
int setkey (char *key)
int encrypt (char *block, int flag)
int des_setkey (const char *key)
int des_cipher (const char *in, char *out, long salt, int count)
The crypt(3) function performs password encryption. It is derived from the NBS Data Encryption Standard. Additional code has been added to deter key search attempts. The first argument to crypt(3) is a NUL-terminated string (normally a password typed by a user). The second is a character array, nine bytes long, consisting of an underscore ("_") followed by four bytes of iteration count and four bytes of salt. Both the iteration count and the salt are encoded with six bits per character, least significant bits first. The values 0 to 63 are encoded by the characters "./0-9A-Za-z", respectively.
The salt is used to induce disorder into the DES algorithm in one of 16777216 possible ways (specifically, if bit i of the salt is set, bits i and i+24 are swapped in the DES "E" box output). The key is divided into groups of eight characters (a short final group is null-padded) and the low-order seven bits of each character (56 bits per group) are used to form the DES key as follows: the first group of 56 bits becomes the initial DES key. For each additional group, the XOR of the group bits and the encryption of the DES key with itself becomes the next DES key. Then the final DES key is used to perform count cumulative encryptions of a 64-bit constant. The value returned is a NUL-terminated string, 20 bytes in length, consisting of the setting followed by the encoded 64-bit encryption.
For compatibility with historical versions of crypt(3), the setting may consist of 2 bytes of salt, encoded as above, in which case an iteration count of 25 is used, fewer perturbations of DES are available, at most 8 characters of key are used, and the returned value is a NUL-terminated string 13 bytes in length.
The functions encrypt(3), setkey(3), des_setkey(3), and des_cipher(3) allow limited access to the DES algorithm itself. The key argument to setkey(3) is a 64 character array of binary values (numeric 0 or 1). A 56-bit key is derived from this array by dividing the array into groups of 8 and ignoring the last bit in each group.
The encrypt(3) argument block is also a 64 character array of binary values. If the value of flag is 0, the argument block is encrypted, otherwise it is decrypted. The encryption or decryption is returned in the original array block after using the key specified by setkey(3) to process it.
The des_setkey(3) and des_cipher(3) functions are faster but less portable than setkey(3) and encrypt(3). The argument to des_setkey(3) is a character array of length 8. The least significant bit in each character is ignored and the next 7 bits of each character are concatenated to yield a 56-bit key. The function des_cipher(3) encrypts (or decrypts if count is negative) the 64-bits stored in the 8 characters at in using abs(3) of count iterations of DES and stores the 64-bit result in the 8 characters at out. The salt specifies perturbations to DES as described above.
The function crypt(3) returns a pointer to the encrypted value on success and NULL on failure. The functions setkey(3), encrypt(3), des_setkey(3), and des_cipher(3) return 0 on success and 1 on failure. Historically, the functions setkey(3) and encrypt(3) did not return any value. They have been provided return values primarily to distinguish implementations where hardware support is provided but not available or where the DES encryption is not available due to the usual political silliness.
On success, crypt(3) returns a pointer to the encoded string. On failure, it returns NULL and sets errno.
The crypt(3) and setkey(3) functions can fail for the following reasons:
Dropping the least significant bit in each character of the argument to des_setkey(3) is ridiculous.
The crypt(3) function leaves its result in an internal static object and returns a pointer to that object. Subsequent calls to crypt(3) will modify the same object.
Due to legal restrictions on the export of cryptographic tools outside of the United States and certain other nations, these calls are not part of the base INTERIX product.
login(1)
passwd(1)
getpass(3)