crypt(3X)
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crypt Subroutine
password and file encryption functions
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SYNTAX
cc [flag ...] file ... -lcrypt
char *crypt (key, salt)
char *key, *salt;
void setkey (key)
char *key;
void encrypt (block, flag)
char *block;
int flag;
char *descrypt (key, salt)
char *key, *salt;
void dessetkey (key)
char *key;
void desencrypt (block, flag)
char *block;
int flag;
int runsetkey (p, key)
int p[2];
char *key;
int runcrypt (offset, buffer, count, p)
long offset;
char *buffer;
unsigned int count;
int p[2];
int cryptclose(p)
int p[2];
DESCRIPTION
des_crypt is the password encryption function. It is based on a
one way hashing encryption algorithm with variations intended
(among other things) to frustrate use of hardware implementations
of a key search.
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crypt(3X)
Key is a user's typed password. Salt is a two-character string
chosen from the set [a-zA-Z0-9./]; this string is used to perturb
the hashing algorithm in one of 4096 different ways, after which
the password is used as the key to encrypt repeatedly a constant
string. The returned value points to the encrypted password.
The first two characters are the salt itself.
The des_setkey and des_encrypt entries provide (rather primitive)
access to the actual hashing algorithm. The argument of
des_setkey is a character array of length 64 containing only the
characters with numerical value 0 and 1. If this string is
divided into groups of 8, the low-order bit in each group is
ignored; this gives a 56-bit key which is set into the machine.
This is the key that will be used with the hashing algorithm to
encrypt the string block with the function des_encrypt.
The argument to the des_encrypt entry is a character array of
length 64 containing only the characters with numerical value 0
and 1. The argument array is modified in place to a similar
array representing the bits of the argument after having been
subjected to the hashing algorithm using the key set by
des_setkey. If edflag is zero, the argument is encrypted; if
non-zero, it is decrypted.
Note that decryption is not provided in the international version
of crypt(3X).
Crypt, setkey, and encrypt are front-end routines that invoke
des_crypt, des_setkey, and des_encrypt respectively.
The routines run_setkey and run_crypt are designed for use by
applications that need cryptographic capabilities [such as ed(1)
and vi(1)] that must be compatible with the crypt(1) user-level
utility. Run_setkey establishes a two-way pipe connection with
crypt(1), using key as the password argument. Run_crypt takes a
block of characters and transforms the cleartext or ciphertext
into their ciphertext or cleartext using crypt(1). Offset is the
relative byte position from the beginning of the file that the
block of text provided in block is coming from. Count is the
number of characters in block, and p is an array containing input
and output descriptors. When encryption is finished, crypt_close
is used to terminate the connection with crypt(1).
Run_setkey returns -1 if a connection with crypt(1) cannot be
established. This will occur on international versions of DG/UX
where crypt(1) is not available. If a null key is passed to
run_setkey, 0 is returned. Otherwise, 1 is returned. Run_crypt
returns -1 if it cannot write output or read input from the pipe
attached to crypt. Otherwise it returns 0.
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crypt(3X)
DIAGNOSTICS
In the international version of crypt(3X), a flag argument of 1
to des_encrypt is not accepted, and an error message is printed.
SEE ALSO
getpass(3C), passwd(4).
crypt(1), login(1), passwd(1) in the User's Reference for the
DG/UX System.
CAVEAT
The return value in crypt points to static data that are
overwritten by each call.
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