[apple/libc.git] / gen / crypt.3

.\" $OpenBSD: crypt.3,v 1.5 1996/12/10 09:06:09 deraadt Exp $
.\"
.\" FreeSec: libcrypt
.\"
.\" Copyright (c) 1994 David Burren
.\" 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.
.\" 4. Neither the name of the author nor the names of other contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
.\"
.\" Manual page, using -mandoc macros
.\"
.Dd March 9, 1994
.Dt CRYPT 3
.Os "FreeSec 1.0"
.Sh NAME
.Nm crypt ,
.Nm setkey ,
.Nm encrypt ,
.Nm des_setkey ,
.Nm des_cipher ,
.Nd DES encryption
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft char
.Fn *crypt "const char *key" "const char *setting"
.Ft void
.Fn setkey "char *key"
.Ft void
.Fn encrypt "char *block" "int flag"
.Ft int
.Fn des_setkey "const char *key"
.Ft int
.Fn des_cipher "const char *in" "char *out" "long salt" "int count"
.Sh DESCRIPTION
The
.Fn crypt
function performs password encryption, based on the
.Tn NBS
Data Encryption Standard (DES).
Additional code has been added to deter key search attempts.
The first argument to
.Fn crypt
is a
.Dv null Ns -terminated
string, typically a user's typed password.
The second is in one of two forms:
if it begins with an underscore (``_'') then an extended format is used
in interpreting both the key and the setting, as outlined below.
.Ss Extended crypt:
.Pp
The
.Ar key
is divided into groups of 8 characters (the last group is null-padded)
and the low-order 7 bits of each 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 encryption of the current DES
key with itself and the group bits becomes the next DES key.
.Pp
The setting is a 9-character array consisting of an underscore followed
by 4 bytes of iteration count and 4 bytes of salt.
These are encoded as printable characters, 6 bits per character,
least significant character first.
The values 0 to 63 are encoded as ``./0-9A-Za-z''.
This allows 24 bits for both
.Fa count
and
.Fa salt .
.Ss "Traditional" crypt:
.Pp
The first 8 bytes of the key are null-padded, and the low-order 7 bits of
each character is used to form the 56-bit
.Tn DES
key.
.Pp
The setting is a 2-character array of the ASCII-encoded salt.
Thus only 12 bits of
.Fa salt
are used.
.Fa count
is set to 25.
.Ss Algorithm:
.Pp
The
.Fa salt
introduces disorder in the
.Tn DES
algorithm in one of 16777216 or 4096 possible ways
(ie. with 24 or 12 bits: if bit
.Em i
of the
.Ar salt
is set, then bits
.Em i
and
.Em i+24
are swapped in the
.Tn DES
E-box output).
.Pp
The DES key is used to encrypt a 64-bit constant using
.Ar count
iterations of
.Tn DES .
The value returned is a
.Dv null Ns -terminated
string, 20 or 13 bytes (plus null) in length, consisting of the
.Ar setting
followed by the encoded 64-bit encryption.
.Pp
The functions,
.Fn encrypt ,
.Fn setkey ,
.Fn des_setkey
and
.Fn des_cipher
provide access to the
.Tn DES
algorithm itself.
.Fn setkey
is passed a 64-byte array of binary values (numeric 0 or 1).
A 56-bit key is extracted from this array by dividing the
array into groups of 8, and ignoring the last bit in each group.
That bit is reserved for a byte parity check by DES, but is ignored
by these functions.
.Pp
The
.Fa block
argument to
.Fn encrypt
is also a 64-byte array of binary values.
If the value of
.Fa flag
is 0,
.Fa block
is encrypted otherwise it is decrypted.
The result is returned in the original array
.Fa block
after using the key specified by
.Fn setkey
to process it.
.Pp
The argument to
.Fn des_setkey
is a character array of length 8.
The least significant bit (the parity bit) in each character is ignored,
and the remaining bits are concatenated to form a 56-bit key.
The function
.Fn des_cipher
encrypts (or decrypts if
.Fa count
is negative) the 64-bits stored in the 8 characters at
.Fa in
using
.Xr abs 3
of
.Fa count
iterations of
.Tn DES
and stores the 64-bit result in the 8 characters at
.Fa out
(which may be the same as
.Fa in
).
The
.Fa salt
specifies perturbations to the
.Tn DES
E-box output as described above.
.Pp
The function
.Fn crypt
returns a pointer to the encrypted value on success, and NULL on failure.
The functions
.Fn setkey ,
.Fn encrypt ,
.Fn des_setkey ,
and
.Fn des_cipher
return 0 on success and 1 on failure.
.Pp
The
.Fn crypt ,
.Fn setkey
and
.Fn des_setkey
functions all manipulate the same key space.
.Sh SEE ALSO
.Xr login 1 ,
.Xr passwd 1 ,
.Xr getpass 3 ,
.Xr passwd 5
.Sh BUGS
The
.Fn crypt
function returns a pointer to static data, and subsequent calls to
.Fn crypt
will modify the same object.
.Sh HISTORY
A rotor-based
.Fn crypt
function appeared in
.At v6 .
The current style
.Fn crypt
first appeared in
.At v7 .
.Pp
This library (FreeSec 1.0) was developed outside the United States of America
as an unencumbered replacement for the U.S.-only libcrypt encryption
library.
Programs linked against the 
.Fn crypt
interface may be exported from the U.S.A. only if they use 
.Fn crypt
solely for authentication purposes and avoid use of
the other programmer interfaces listed above. Special care has been taken
in the library so that programs which only use the 
.Fn crypt
interface do not pull in the other components.
.Sh AUTHOR
David Burren <davidb@werj.com.au>
Commit	Line	Data
59e0d9fe A	1	.\" $OpenBSD: crypt.3,v 1.5 1996/12/10 09:06:09 deraadt Exp $
	2	.\"
	3	.\" FreeSec: libcrypt
	4	.\"
	5	.\" Copyright (c) 1994 David Burren
	6	.\" All rights reserved.
	7	.\"
	8	.\" Redistribution and use in source and binary forms, with or without
	9	.\" modification, are permitted provided that the following conditions
	10	.\" are met:
	11	.\" 1. Redistributions of source code must retain the above copyright
	12	.\" notice, this list of conditions and the following disclaimer.
	13	.\" 2. Redistributions in binary form must reproduce the above copyright
	14	.\" notice, this list of conditions and the following disclaimer in the
	15	.\" documentation and/or other materials provided with the distribution.
	16	.\" 4. Neither the name of the author nor the names of other contributors
	17	.\" may be used to endorse or promote products derived from this software
	18	.\" without specific prior written permission.
	19	.\"
	20	.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
	21	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	22	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	23	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
	24	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	25	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	26	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	27	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	28	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	29	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	30	.\" SUCH DAMAGE.
	31	.\"
	32	.\" Manual page, using -mandoc macros
	33	.\"
	34	.Dd March 9, 1994
	35	.Dt CRYPT 3
	36	.Os "FreeSec 1.0"
	37	.Sh NAME
	38	.Nm crypt ,
	39	.Nm setkey ,
	40	.Nm encrypt ,
	41	.Nm des_setkey ,
	42	.Nm des_cipher ,
	43	.Nd DES encryption
	44	.Sh SYNOPSIS
	45	.Fd #include <unistd.h>
	46	.Ft char
	47	.Fn crypt "const char key" "const char *setting"
	48	.Ft void
	49	.Fn setkey "char *key"
	50	.Ft void
	51	.Fn encrypt "char *block" "int flag"
	52	.Ft int
	53	.Fn des_setkey "const char *key"
	54	.Ft int
	55	.Fn des_cipher "const char in" "char out" "long salt" "int count"
	56	.Sh DESCRIPTION
	57	The
	58	.Fn crypt
	59	function performs password encryption, based on the
	60	.Tn NBS
	61	Data Encryption Standard (DES).
	62	Additional code has been added to deter key search attempts.
	63	The first argument to
	64	.Fn crypt
65	is a
66	.Dv null Ns -terminated
67	string, typically a user's typed password.
68	The second is in one of two forms:
69	if it begins with an underscore (``_'') then an extended format is used
70	in interpreting both the key and the setting, as outlined below.
71	.Ss Extended crypt:
72	.Pp
73	The
74	.Ar key
75	is divided into groups of 8 characters (the last group is null-padded)
76	and the low-order 7 bits of each each character (56 bits per group) are
77	used to form the DES key as follows:
78	the first group of 56 bits becomes the initial DES key.
79	For each additional group, the XOR of the encryption of the current DES
80	key with itself and the group bits becomes the next DES key.
81	.Pp
82	The setting is a 9-character array consisting of an underscore followed
83	by 4 bytes of iteration count and 4 bytes of salt.
84	These are encoded as printable characters, 6 bits per character,
85	least significant character first.
86	The values 0 to 63 are encoded as ``./0-9A-Za-z''.
87	This allows 24 bits for both
88	.Fa count
89	and
90	.Fa salt .
91	.Ss "Traditional" crypt:
92	.Pp
93	The first 8 bytes of the key are null-padded, and the low-order 7 bits of
94	each character is used to form the 56-bit
95	.Tn DES
96	key.
97	.Pp
98	The setting is a 2-character array of the ASCII-encoded salt.
99	Thus only 12 bits of
100	.Fa salt
101	are used.
102	.Fa count
103	is set to 25.
104	.Ss Algorithm:
105	.Pp
106	The
107	.Fa salt
108	introduces disorder in the
109	.Tn DES
110	algorithm in one of 16777216 or 4096 possible ways
111	(ie. with 24 or 12 bits: if bit
112	.Em i
113	of the
114	.Ar salt
115	is set, then bits
116	.Em i
117	and
118	.Em i+24
119	are swapped in the
120	.Tn DES
121	E-box output).
122	.Pp
123	The DES key is used to encrypt a 64-bit constant using
124	.Ar count
125	iterations of
126	.Tn DES .
127	The value returned is a
128	.Dv null Ns -terminated
129	string, 20 or 13 bytes (plus null) in length, consisting of the
130	.Ar setting
131	followed by the encoded 64-bit encryption.
132	.Pp
133	The functions,
134	.Fn encrypt ,
135	.Fn setkey ,
136	.Fn des_setkey
137	and
138	.Fn des_cipher
139	provide access to the
140	.Tn DES
141	algorithm itself.
142	.Fn setkey
143	is passed a 64-byte array of binary values (numeric 0 or 1).
144	A 56-bit key is extracted from this array by dividing the
145	array into groups of 8, and ignoring the last bit in each group.
146	That bit is reserved for a byte parity check by DES, but is ignored
147	by these functions.
148	.Pp
149	The
150	.Fa block
151	argument to
152	.Fn encrypt
153	is also a 64-byte array of binary values.
154	If the value of
155	.Fa flag
156	is 0,
157	.Fa block
158	is encrypted otherwise it is decrypted.
159	The result is returned in the original array
160	.Fa block
161	after using the key specified by
162	.Fn setkey
163	to process it.
164	.Pp
165	The argument to
166	.Fn des_setkey
167	is a character array of length 8.
168	The least significant bit (the parity bit) in each character is ignored,
169	and the remaining bits are concatenated to form a 56-bit key.
170	The function
171	.Fn des_cipher
172	encrypts (or decrypts if
173	.Fa count
174	is negative) the 64-bits stored in the 8 characters at
175	.Fa in
176	using
177	.Xr abs 3
178	of
179	.Fa count
180	iterations of
181	.Tn DES
182	and stores the 64-bit result in the 8 characters at
183	.Fa out
184	(which may be the same as
185	.Fa in
186	).
187	The
188	.Fa salt
189	specifies perturbations to the
190	.Tn DES
191	E-box output as described above.
192	.Pp
193	The function
194	.Fn crypt
195	returns a pointer to the encrypted value on success, and NULL on failure.
196	The functions
197	.Fn setkey ,
198	.Fn encrypt ,
199	.Fn des_setkey ,
200	and
201	.Fn des_cipher
202	return 0 on success and 1 on failure.
203	.Pp
204	The
205	.Fn crypt ,
206	.Fn setkey
207	and
208	.Fn des_setkey
209	functions all manipulate the same key space.
210	.Sh SEE ALSO
211	.Xr login 1 ,
212	.Xr passwd 1 ,
213	.Xr getpass 3 ,
214	.Xr passwd 5
215	.Sh BUGS
216	The
217	.Fn crypt
218	function returns a pointer to static data, and subsequent calls to
219	.Fn crypt
220	will modify the same object.
221	.Sh HISTORY
222	A rotor-based
223	.Fn crypt
224	function appeared in
225	.At v6 .
226	The current style
227	.Fn crypt
228	first appeared in
229	.At v7 .
230	.Pp
231	This library (FreeSec 1.0) was developed outside the United States of America
232	as an unencumbered replacement for the U.S.-only libcrypt encryption
233	library.
234	Programs linked against the
235	.Fn crypt
236	interface may be exported from the U.S.A. only if they use
237	.Fn crypt
238	solely for authentication purposes and avoid use of
239	the other programmer interfaces listed above. Special care has been taken
240	in the library so that programs which only use the
241	.Fn crypt
242	interface do not pull in the other components.
243	.Sh AUTHOR
244	David Burren <davidb@werj.com.au>