1 .\" FreeSec: libcrypt for NetBSD
3 .\" Copyright (c) 1994 David Burren
4 .\" All rights reserved.
6 .\" Redistribution and use in source and binary forms, with or without
7 .\" modification, are permitted provided that the following conditions
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18 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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30 .\" $FreeBSD: src/lib/libcrypt/crypt.3,v 1.6.2.14 2002/12/29 16:35:35 schweikh Exp $
31 .\" $DragonFly: src/lib/libcrypt/crypt.3,v 1.2 2003/06/17 04:26:49 dillon Exp $
33 .\" Manual page, using -mandoc macros
40 .Nd Trapdoor encryption
46 .Fn crypt "const char *key" "const char *salt"
48 .Fn crypt_get_format "void"
50 .Fn crypt_set_format "const char *string"
54 function performs password hashing with additional code added to
55 deter key search attempts. Different algorithms can be used to
59 .\" If you add more algorithms, make sure to update this list
60 .\" and the default used for the Traditional format, below.
62 Currently these include the
64 .Tn Data Encryption Standard (DES) ,
68 The algorithm used will depend upon the format of the Salt (following
69 the Modular Crypt Format (MCF)), if
73 is installed or not, and whether
75 has been called to change the default.
79 is the data to hash (usually a password), in a
80 .Dv null Ns -terminated
82 The second is the salt, in one of three forms:
84 .Bl -tag -width Traditional -compact -offset indent
86 If it begins with an underscore
91 is used in interpreting both the key and the salt, as outlined below.
93 If it begins with the string
95 then the Modular Crypt Format is used, as outlined below.
97 If neither of the above is true, it assumes the Traditional Format,
98 using the entire string as the salt (or the first portion).
101 All routines are designed to be time-consuming. A brief test on a
105 crypt to do approximately 2640 crypts
106 a CPU second and MD5 to do about 62 crypts a CPU second.
107 .Ss DES Extended Format:
111 is divided into groups of 8 characters (the last group is null-padded)
112 and the low-order 7 bits of each character (56 bits per group) are
116 the first group of 56 bits becomes the initial
119 For each additional group, the XOR of the encryption of the current
121 key with itself and the group bits becomes the next
125 The salt is a 9-character array consisting of an underscore followed
126 by 4 bytes of iteration count and 4 bytes of salt.
127 These are encoded as printable characters, 6 bits per character,
128 least significant character first.
129 The values 0 to 63 are encoded as ``./0-9A-Za-z''.
130 This allows 24 bits for both
137 introduces disorder in the
139 algorithm in one of 16777216 or 4096 possible ways
140 (ie. with 24 or 12 bits: if bit
154 key is used to encrypt a 64-bit constant using
158 The value returned is a
159 .Dv null Ns -terminated
160 string, 20 or 13 bytes (plus null) in length, consisting of the
162 followed by the encoded 64-bit encryption.
165 If the salt begins with the string
167 then the Modular Crypt Format is used. The
169 represents which algorithm is used in encryption. Following the token is
170 the actual salt to use in the encryption. The length of the salt is limited
171 to 8 characters--because the length of the returned output is also limited
172 (_PASSWORD_LEN). The salt must be terminated with the end of the string
173 (NULL) or a dollar sign. Any characters after the dollar sign are ignored.
175 Currently supported algorithms are:
177 .Bl -enum -compact -offset indent
184 Other crypt formats may be easily added. An example salt would be:
185 .Bl -tag -offset indent
186 .It Cm "$3$thesalt$rest"
189 .Ss "Traditional" crypt:
191 The algorithm used will depend upon whether
193 has been called and whether a global default format has been specified.
194 Unless a global default has been specified or
196 has set the format to something else, the built-in default format is
200 .\" NOTICE: Also make sure to update this
203 if it is available, or MD5 if not.
205 How the salt is used will depend upon the algorithm for the hash. For
206 best results, specify at least two characters of salt.
210 function returns a constant string that represents the name of the
211 algorithm currently used.
214 .\" NOTICE: Also make sure to update this, too, as well
223 function sets the default encoding format according to the supplied
226 The global default format can be set using the
233 returns a pointer to the encrypted value on success, and NULL on failure.
234 Note: this is not a standard behaviour, AT&T
236 will always return a pointer to a string.
239 will return 1 if the supplied encoding format was valid.
240 Otherwise, a value of 0 is returned.
252 function returns a pointer to static data, and subsequent calls to
254 will modify the same data. Likewise,
256 modifies static data.
269 section of the code (FreeSec 1.0) was developed outside the United
270 States of America as an unencumbered replacement for the U.S.-only
272 libcrypt encryption library.
275 Originally written by
276 .An David Burren Aq davidb@werj.com.au ,
277 later additions and changes by
278 .An Poul-Henning Kamp ,
279 .An Mark R V Murray ,