3 cfa37a7b 2004-04-10 devnull setupDESstate, des_key_setup, block_cipher, desCBCencrypt, desCBCdecrypt, desECBencrypt, desECBdecrypt, des3CBCencrypt, des3CBCdecrypt, des3ECBencrypt, des3ECBdecrypt, key_setup, des56to64, des64to56, setupDES3state, triple_block_cipher, - single and triple digital encryption standard
4 cfa37a7b 2004-04-10 devnull .SH SYNOPSIS
5 cfa37a7b 2004-04-10 devnull .B #include <u.h>
7 cfa37a7b 2004-04-10 devnull .B #include <libc.h>
9 cfa37a7b 2004-04-10 devnull .B #include <mp.h>
11 cfa37a7b 2004-04-10 devnull .B #include <libsec.h>
14 cfa37a7b 2004-04-10 devnull void des_key_setup(uchar key[8], ulong schedule[32])
17 cfa37a7b 2004-04-10 devnull void block_cipher(ulong *schedule, uchar *data,
19 cfa37a7b 2004-04-10 devnull int decrypting)
22 cfa37a7b 2004-04-10 devnull void setupDESstate(DESstate *s, uchar key[8], uchar *ivec)
25 cfa37a7b 2004-04-10 devnull void desCBCencrypt(uchar*, int, DESstate*)
28 cfa37a7b 2004-04-10 devnull void desCBCdecrypt(uchar*, int, DESstate*)
31 cfa37a7b 2004-04-10 devnull void desECBencrypt(uchar*, int, DESstate*)
34 cfa37a7b 2004-04-10 devnull void desECBdecrypt(uchar*, int, DESstate*)
37 cfa37a7b 2004-04-10 devnull void triple_block_cipher(ulong keys[3][32], uchar*, int)
40 cfa37a7b 2004-04-10 devnull void setupDES3state(DES3state *s, uchar key[3][8],
42 cfa37a7b 2004-04-10 devnull uchar *ivec)
45 cfa37a7b 2004-04-10 devnull void des3CBCencrypt(uchar*, int, DES3state*)
48 cfa37a7b 2004-04-10 devnull void des3CBCdecrypt(uchar*, int, DES3state*)
51 cfa37a7b 2004-04-10 devnull void des3ECBencrypt(uchar*, int, DES3state*)
54 cfa37a7b 2004-04-10 devnull void des3ECBdecrypt(uchar*, int, DES3state*)
57 cfa37a7b 2004-04-10 devnull void key_setup(uchar[7], ulong[32])
60 cfa37a7b 2004-04-10 devnull void des56to64(uchar *k56, uchar *k64)
63 cfa37a7b 2004-04-10 devnull void des64to56(uchar *k64, uchar *k56)
64 cfa37a7b 2004-04-10 devnull .SH DESCRIPTION
66 cfa37a7b 2004-04-10 devnull The Digital Encryption Standard (DES)
67 cfa37a7b 2004-04-10 devnull is a shared key or symmetric encryption using either
68 cfa37a7b 2004-04-10 devnull a 56 bit key for single DES or three 56 bit keys for triple des.
69 cfa37a7b 2004-04-10 devnull The keys are encoded into 64 bits where every eight bit
70 cfa37a7b 2004-04-10 devnull is parity.
72 cfa37a7b 2004-04-10 devnull The basic DES function,
73 cfa37a7b 2004-04-10 devnull .IR block_cipher ,
74 cfa37a7b 2004-04-10 devnull works on a block of 8 bytes, converting them in place.
75 cfa37a7b 2004-04-10 devnull It takes a key schedule, a pointer to the block, and
76 cfa37a7b 2004-04-10 devnull a flag indicating encrypting (0) or decrypting (1).
77 cfa37a7b 2004-04-10 devnull The key schedule is created from the key using
78 cfa37a7b 2004-04-10 devnull .IR des_key_setup .
80 cfa37a7b 2004-04-10 devnull Since it is a bit awkward,
81 cfa37a7b 2004-04-10 devnull .I block_cipher
82 cfa37a7b 2004-04-10 devnull is rarely called directly. Instead, one normally uses
83 cfa37a7b 2004-04-10 devnull routines that encrypt larger buffers of data and
84 cfa37a7b 2004-04-10 devnull which may chain the encryption state from one buffer
85 cfa37a7b 2004-04-10 devnull to the next.
86 cfa37a7b 2004-04-10 devnull These routines keep track of the state of the
87 cfa37a7b 2004-04-10 devnull encryption using a
88 cfa37a7b 2004-04-10 devnull .B DESstate
89 cfa37a7b 2004-04-10 devnull structure that contains the key schedule and any chained
91 cfa37a7b 2004-04-10 devnull .I SetupDESstate
92 cfa37a7b 2004-04-10 devnull sets up the
93 cfa37a7b 2004-04-10 devnull .B DESstate
94 cfa37a7b 2004-04-10 devnull structure using the key and an 8 byte initialization vector.
96 cfa37a7b 2004-04-10 devnull Electronic code book, using
97 cfa37a7b 2004-04-10 devnull .I desECBencrypt
99 cfa37a7b 2004-04-10 devnull .IR desECBdecrypt ,
100 cfa37a7b 2004-04-10 devnull is the less secure mode. The encryption of each 8 bytes
101 cfa37a7b 2004-04-10 devnull does not depend on the encryption of any other.
102 cfa37a7b 2004-04-10 devnull Hence the encryption is a substitution
103 cfa37a7b 2004-04-10 devnull cipher using 64 bit characters.
105 cfa37a7b 2004-04-10 devnull Cipher block chaining mode, using
106 cfa37a7b 2004-04-10 devnull .I desCBCencrypt
108 cfa37a7b 2004-04-10 devnull .IR desCBCdecrypt ,
109 cfa37a7b 2004-04-10 devnull is more secure. Every block encrypted depends on the initialization
110 cfa37a7b 2004-04-10 devnull vector and all blocks encrypted before it.
112 cfa37a7b 2004-04-10 devnull For both CBC and ECB modes, a stream of data can be encrypted as
113 cfa37a7b 2004-04-10 devnull multiple buffers. However, all buffers except the last must
114 cfa37a7b 2004-04-10 devnull be a multiple of 8 bytes to ensure successful decryption of
115 cfa37a7b 2004-04-10 devnull the stream.
117 cfa37a7b 2004-04-10 devnull There are equivalent triple DES functions for each of the
118 cfa37a7b 2004-04-10 devnull DES functions.
120 cfa37a7b 2004-04-10 devnull In the past Plan 9 used a 56 bit or 7 byte
121 cfa37a7b 2004-04-10 devnull format for DES keys. To be compatible with the rest
122 cfa37a7b 2004-04-10 devnull of the world, we've abandoned this format.
123 cfa37a7b 2004-04-10 devnull There are two functions:
124 cfa37a7b 2004-04-10 devnull .I des56to64
126 cfa37a7b 2004-04-10 devnull .I des64to56
127 cfa37a7b 2004-04-10 devnull to convert back and forth between the two formats.
128 cfa37a7b 2004-04-10 devnull Also a key schedule can be set up from the 7 byte format
130 cfa37a7b 2004-04-10 devnull .IR key_setup .
132 cfa37a7b 2004-04-10 devnull .SH SOURCE
133 c3674de4 2005-01-11 devnull .B \*9/src/libsec
134 cfa37a7b 2004-04-10 devnull .SH SEE ALSO
135 d32deab1 2020-08-16 rsc .MR mp (3) ,
136 d32deab1 2020-08-16 rsc .MR aes (3) ,
137 d32deab1 2020-08-16 rsc .MR blowfish (3) ,
138 d32deab1 2020-08-16 rsc .MR dsa (3) ,
139 d32deab1 2020-08-16 rsc .MR elgamal (3) ,
140 d32deab1 2020-08-16 rsc .MR rc4 (3) ,
141 d32deab1 2020-08-16 rsc .MR rsa (3) ,
142 d32deab1 2020-08-16 rsc .MR sechash (3) ,
143 d32deab1 2020-08-16 rsc .MR prime (3) ,
144 d32deab1 2020-08-16 rsc .MR rand (3)
