10564b1175
groff 1.23.0 added .MR to its -man macro package. The NEWS file states
that the inclusion of the macro "was prompted by its introduction to
Plan 9 from User Space's troff in August 2020." From d32deab it seems
that the name for Plan 9 from User Space's implementation was suggested
by groff maintainer G. Brandon Robinson.
Not sure if the intention was to make these definitions compatible, but
it would be nice if they were.
Currently, Plan 9 from User Space's .MR expects its second argument to
be parenthesized. groff's .MR does not. This results in extra
parentheses appearing in manual references when viewing Plan 9 from User
Space's manual pages on a system using groff.
145 lines
3.4 KiB
Groff
145 lines
3.4 KiB
Groff
.TH DES 3
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.SH NAME
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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
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.SH SYNOPSIS
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.B #include <u.h>
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.br
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.B #include <libc.h>
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.br
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.B #include <mp.h>
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.br
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.B #include <libsec.h>
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.PP
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.B
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void des_key_setup(uchar key[8], ulong schedule[32])
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.PP
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.B
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void block_cipher(ulong *schedule, uchar *data,
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.B
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int decrypting)
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.PP
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.B
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void setupDESstate(DESstate *s, uchar key[8], uchar *ivec)
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.PP
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.B
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void desCBCencrypt(uchar*, int, DESstate*)
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.PP
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.B
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void desCBCdecrypt(uchar*, int, DESstate*)
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.PP
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.B
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void desECBencrypt(uchar*, int, DESstate*)
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.PP
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.B
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void desECBdecrypt(uchar*, int, DESstate*)
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.PP
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.B
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void triple_block_cipher(ulong keys[3][32], uchar*, int)
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.PP
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.B
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void setupDES3state(DES3state *s, uchar key[3][8],
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.B
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uchar *ivec)
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.PP
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.B
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void des3CBCencrypt(uchar*, int, DES3state*)
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.PP
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.B
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void des3CBCdecrypt(uchar*, int, DES3state*)
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.PP
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.B
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void des3ECBencrypt(uchar*, int, DES3state*)
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.PP
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.B
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void des3ECBdecrypt(uchar*, int, DES3state*)
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.PP
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.B
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void key_setup(uchar[7], ulong[32])
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.PP
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.B
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void des56to64(uchar *k56, uchar *k64)
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.PP
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.B
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void des64to56(uchar *k64, uchar *k56)
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.SH DESCRIPTION
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.PP
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The Digital Encryption Standard (DES)
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is a shared key or symmetric encryption using either
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a 56 bit key for single DES or three 56 bit keys for triple des.
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The keys are encoded into 64 bits where every eight bit
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is parity.
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.PP
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The basic DES function,
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.IR block_cipher ,
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works on a block of 8 bytes, converting them in place.
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It takes a key schedule, a pointer to the block, and
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a flag indicating encrypting (0) or decrypting (1).
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The key schedule is created from the key using
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.IR des_key_setup .
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.PP
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Since it is a bit awkward,
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.I block_cipher
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is rarely called directly. Instead, one normally uses
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routines that encrypt larger buffers of data and
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which may chain the encryption state from one buffer
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to the next.
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These routines keep track of the state of the
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encryption using a
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.B DESstate
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structure that contains the key schedule and any chained
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state.
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.I SetupDESstate
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sets up the
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.B DESstate
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structure using the key and an 8 byte initialization vector.
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.PP
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Electronic code book, using
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.I desECBencrypt
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and
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.IR desECBdecrypt ,
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is the less secure mode. The encryption of each 8 bytes
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does not depend on the encryption of any other.
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Hence the encryption is a substitution
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cipher using 64 bit characters.
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.PP
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Cipher block chaining mode, using
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.I desCBCencrypt
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and
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.IR desCBCdecrypt ,
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is more secure. Every block encrypted depends on the initialization
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vector and all blocks encrypted before it.
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.PP
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For both CBC and ECB modes, a stream of data can be encrypted as
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multiple buffers. However, all buffers except the last must
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be a multiple of 8 bytes to ensure successful decryption of
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the stream.
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.PP
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There are equivalent triple DES functions for each of the
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DES functions.
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.PP
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In the past Plan 9 used a 56 bit or 7 byte
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format for DES keys. To be compatible with the rest
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of the world, we've abandoned this format.
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There are two functions:
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.I des56to64
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and
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.I des64to56
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to convert back and forth between the two formats.
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Also a key schedule can be set up from the 7 byte format
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using
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.IR key_setup .
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.PP
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.SH SOURCE
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.B \*9/src/libsec
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.SH SEE ALSO
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.MR mp 3 ,
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.MR aes 3 ,
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.MR blowfish 3 ,
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.MR dsa 3 ,
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.MR elgamal 3 ,
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.MR rc4 3 ,
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.MR rsa 3 ,
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.MR sechash 3 ,
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.MR prime 3 ,
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.MR rand 3
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