1 .\" Copyright (c) 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" This code is derived from software contributed to Berkeley by
5 .\" Matt Bishop of Dartmouth College.
7 .\" Redistribution and use in source and binary forms, with or without
8 .\" modification, are permitted provided that the following conditions
10 .\" 1. Redistributions of source code must retain the above copyright
11 .\" notice, this list of conditions and the following disclaimer.
12 .\" 2. Redistributions in binary form must reproduce the above copyright
13 .\" notice, this list of conditions and the following disclaimer in the
14 .\" documentation and/or other materials provided with the distribution.
15 .\" 3. All advertising materials mentioning features or use of this software
16 .\" must display the following acknowledgement:
17 .\" This product includes software developed by the University of
18 .\" California, Berkeley and its contributors.
19 .\" 4. Neither the name of the University nor the names of its contributors
20 .\" may be used to endorse or promote products derived from this software
21 .\" without specific prior written permission.
23 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 .\" @(#)bdes.1 8.1 (Berkeley) 6/29/93
36 .\" $FreeBSD: src/secure/usr.bin/bdes/bdes.1,v 1.2.8.2 2001/01/16 15:36:41 ru Exp $
43 .Nd "encrypt/decrypt using the Data Encryption Standard"
57 modes of operation described in
59 including alternative cipher feedback mode and both authentication
62 reads from the standard input and writes to the standard output.
63 By default, the input is encrypted using cipher block chaining mode.
64 Using the same key for encryption and decryption preserves plain text.
66 All modes but the electronic code book mode require an initialization
67 vector; if none is supplied, the zero vector is used.
70 is specified on the command line, the user is prompted for one (see
74 The options are as follows:
75 .Bl -tag -width indent
77 The key and initialization vector strings are to be taken as
79 suppressing the special interpretation given to leading
88 the key and initialization vector.
90 Use electronic code book mode.
96 alternative cipher feedback mode.
99 must be a multiple of 7 between 7 and 56 inclusive (this does not conform
100 to the alternative CFB mode specification).
104 cipher feedback mode.
107 must be a multiple of 8 between 8 and 64 inclusive (this does not conform
108 to the standard CFB mode specification).
112 as the cryptographic key.
114 Compute a message authentication code (MAC) of
119 must be between 1 and 64 inclusive; if
121 is not a multiple of 8, enough 0 bits will be added to pad the MAC length
122 to the nearest multiple of 8.
123 Only the MAC is output.
124 MACs are only available in cipher block chaining mode or in cipher feedback
129 output feedback mode.
132 must be a multiple of 8 between 8 and 64 inclusive (this does not conform
133 to the OFB mode specification).
135 Disable the resetting of the parity bit.
136 This flag forces the parity bit of the key to be used as typed, rather than
137 making each character be of odd parity.
138 It is used only if the key is given in
141 Set the initialization vector to
143 the vector is interpreted in the same way as the key.
144 The vector is ignored in electronic codebook mode.
147 The key and initialization vector are taken as sequences of
149 characters which are then mapped into their bit representations.
150 If either begins with
154 that one is taken as a sequence of hexadecimal digits indicating the
156 if either begins with
160 that one is taken as a sequence of binary digits indicating the bit pattern.
162 only the leading 64 bits of the key or initialization vector
164 and if fewer than 64 bits are provided, enough 0 bits are appended
165 to pad the key to 64 bits.
169 standard, the low-order bit of each character in the
170 key string is deleted.
173 representations set the high-order bit to 0, simply
174 deleting the low-order bit effectively reduces the size of the key space
175 from 2^56 to 2^48 keys.
176 To prevent this, the high-order bit must be a function depending in part
177 upon the low-order bit; so, the high-order bit is set to whatever value
179 This preserves the key space size.
180 Note this resetting of the parity bit is
182 done if the key is given in binary or hex, and can be disabled for
188 is considered a very strong cryptosystem, and other than table lookup
189 attacks, key search attacks, and Hellman's time-memory tradeoff (all of which
190 are very expensive and time-consuming), no cryptanalytic methods for breaking
193 are known in the open literature.
194 No doubt the choice of keys and key security are the most vulnerable aspect
197 .Sh IMPLEMENTATION NOTES
198 For implementors wishing to write software compatible with this program,
199 the following notes are provided.
200 This software is believed to be compatible with the implementation of the
201 data encryption standard distributed by Sun Microsystems, Inc.
203 In the ECB and CBC modes, plaintext is encrypted in units of 64 bits (8 bytes,
204 also called a block).
205 To ensure that the plaintext file is encrypted correctly,
207 will (internally) append from 1 to 8 bytes, the last byte containing an
208 integer stating how many bytes of that final block are from the plaintext
209 file, and encrypt the resulting block.
210 Hence, when decrypting, the last block may contain from 0 to 7 characters
211 present in the plaintext file, and the last byte tells how many.
212 Note that if during decryption the last byte of the file does not contain an
213 integer between 0 and 7, either the file has been corrupted or an incorrect
215 A similar mechanism is used for the OFB and CFB modes, except that those
216 simply require the length of the input to be a multiple of the mode size,
217 and the final byte contains an integer between 0 and one less than the number
218 of bytes being used as the mode.
219 (This was another reason that the mode size must be a multiple of 8 for those
222 Unlike Sun's implementation, unused bytes of that last block are not filled
223 with random data, but instead contain what was in those byte positions in
225 This is quicker and more portable, and does not weaken the encryption
228 If the key is entered in
230 the parity bits of the key characters are set
231 so that each key character is of odd parity.
232 Unlike Sun's implementation, it is possible to enter binary or hexadecimal
233 keys on the command line, and if this is done, the parity bits are
236 This allows testing using arbitrary bit patterns as keys.
238 The Sun implementation always uses an initialization vector of 0
239 (that is, all zeroes).
242 does too, but this may be changed from the command line.
247 .%T "Data Encryption Standard"
248 .%R "Federal Information Processing Standard #46"
249 .%Q "National Bureau of Standards, U.S. Department of Commerce, Washington DC"
253 .%T "DES Modes of Operation"
254 .%R "Federal Information Processing Standard #81"
255 .%Q "National Bureau of Standards, U.S. Department of Commerce, Washington DC"
259 .%A "Dorothy Denning"
260 .%B "Cryptography and Data Security"
261 .%Q "Addison-Wesley Publishing Co., Reading, MA"
266 .%T "Implementation Notes on bdes(1)"
267 .%R "Technical Report PCS-TR-91-158"
268 .%Q "Department of Mathematics and Computer Science, Dartmouth College, Hanover, NH 03755"
273 THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
274 ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
275 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
276 ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
277 FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
278 DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
279 OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
280 HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
281 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
282 OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
286 There is a controversy raging over whether the
290 The advent of special-purpose hardware could reduce the cost of any of the
291 methods of attack named above so that they are no longer computationally
294 As the key or key schedule is stored in memory, the encryption can be
295 compromised if memory is readable.
296 Additionally, programs which display programs' arguments may compromise the
297 key and initialization vector, if they are specified on the command line.
300 overwrites its arguments, however, the obvious race cannot currently be
303 Certain specific keys should be avoided because they introduce potential
304 weaknesses; these keys, called the
308 keys, are (in hex notation, where
310 is either 0 or 1, and
316 .Bl -column "0x0p0p0p0p0p0p0p0p" -offset indent
317 .It "0x0p0p0p0p0p0p0p0p 0x0p1P0p1P0p0P0p0P"
318 .It "0x0pep0pep0pfp0pfp 0x0pfP0pfP0pfP0pfP"
319 .It "0x1P0p1P0p0P0p0P0p 0x1P1P1P1P0P0P0P0P"
320 .It "0x1Pep1Pep0Pfp0Pfp 0x1PfP1PfP0PfP0PfP"
321 .It "0xep0pep0pfp0pfp0p 0xep1Pep1pfp0Pfp0P"
322 .It "0xepepepepepepepep 0xepfPepfPfpfPfpfP"
323 .It "0xfP0pfP0pfP0pfP0p 0xfP1PfP1PfP0PfP0P"
324 .It "0xfPepfPepfPepfPep 0xfPfPfPfPfPfPfPfP"
327 This is inherent in the
333 .%T "Cycle structure of the DES with weak and semi-weak keys"
334 .%B "Advances in Cryptology \- Crypto '86 Proceedings"
335 .%Q "Springer-Verlag New York"