.\" Copyright (c) 1989, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)crypt.3 8.2 (Berkeley) 12/11/93 .\" .TH CRYPT 3 "28 January 1997" GNO "Library Routines" .SH NAME .BR crypt , .BR setkey , .BR encrypt , \- simple encryption .SH SYNOPSIS #include .sp 1 char *\fBcrypt\fR (const char *\fIkey\fR, const char *\fIsalt\fR); .br int \fBsetkey\fR (char *\fIkey\fR); .br int \fBencrypt\fR (char *\fIblock\fR, int \fIflag\fR); .SH DESCRIPTION The .BR crypt function performs password encryption. It is derived from an algorithm given in .I "Computer Networks" by Andy Tanenbaum. .LP The first argument to .BR crypt .RI ( key ) is a .BR NULL -terminated string (normally a password typed by a user). The second, .IR salt , is a two-character array that should be randomly generated by the caller in the case of encrypting a new password, or should be taken as the first two characters of the .BR /etc/passwd password entry in the case of validating a password. .LP The functions, .BR encrypt and .BR setkey allow limited access to the encryption algorithm itself. The .IR key argument to .BR setkey 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. .LP The .BR encrypt argument .I block is also a 64 character array of binary values. If the value of .I flag is 0, the argument .I block is encrypted, otherwise it is decrypted. The encryption or decryption is returned in the original array .I block after using the key specified by .BR setkey to process it. .LP The function .BR crypt returns a pointer to the encrypted value (which is formatted as printable ASCII characters) on success and NULL on failure. The functions .BR setkey and .BR encrypt return 0 on success and 1 on failure. .LP Use of these routines requires linking with the .BR libcrypt library. .SH SEE ALSO .BR login (1), .BR passwd (1), .BR getpass (3), .BR passwd (5) .sp .RS .I "Mathematical Cryptology for Computer Scientists and Mathematicians" by Wayne Patterson. 1987. Volume ISBN 0-8476-7438-X. .RE .sp 1 .RS .I "Password Security: A Case History" by R. Morris, Ken Thompson. .IR "Communications of the ACM" , vol. 22, pp. 594-597. November 1979. .RE .sp 1 .RS .I "DES will be Totally Insecure within Ten Years" by M.E. Hellman. .IR "IEEE Spectrum" , vol. 16, pp. 32-39. July 1979. .RE .SH BUGS The .BR crypt function leaves its result in an internal static object and returns a pointer to that object. Subsequent calls to .BR crypt will modify the same object.