102 lines
2 KiB
Text
102 lines
2 KiB
Text
.TH SALSA 2
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.SH NAME
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setupSalsastate, salsa_setblock, salsa_setiv, salsa_encrypt, salsa_encrypt2, hsalsa
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\- salsa20 encryption
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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 <libsec.h>
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.PP
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.B
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void setupSalsastate(Salsastate *s, uchar key[], ulong keylen, uchar *iv, ulong ivlen, int rounds)
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.PP
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.B
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void salsa_encrypt(uchar *data, ulong len, Salsastate *s)
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.PP
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.B
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void salsa_encrypt2(uchar *src, uchar *dst, ulong len, Salsastate *s)
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.PP
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.B
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void salsa_setblock(Salsastate *s, u64int blockno)
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.PP
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.B
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void salsa_setiv(Salsastate *s, uchar *iv);
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.PP
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.B
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void hsalsa(uchar h[32], uchar *key, ulong keylen, uchar nonce[16], int rounds);
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.SH DESCRIPTION
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.PP
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Salsa20 is a stream cipher designed by D J Berstein. It has an underlying block size of 64 bytes
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(named as constant
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.BR SalsaBsize ).
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It supports key sizes of 128 and 256-bit (recommended).
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.PP
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.I SetupSalsastate
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takes a reference to a
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.B Salsastate
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structure, a
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.I key
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of
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.I keylen
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bytes, which should normally be
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.BR SalsaKeylen = 32 ,
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a
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.I iv
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or nonce of
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.I ivlen
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bytes (can be
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.BR SalsaIVlen = 8
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or
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.BR XSalsaIVlen = 24 ,
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set to all zeros if the
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.I iv
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argument is nil),
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and the number of
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.I rounds
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(set to the default of 20 if the argument is zero).
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.PP
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.I Salsa_encrypt
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encrypts
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.I len
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bytes of
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.I buf
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in place using the
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.B Salsastate
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in
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.IR s .
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.I Len
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can be any byte length.
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Encryption and decryption are the same operation given the same starting state
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.IR s .
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.PP
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.I Salsa_encrypt2
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is similar, but encrypts
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.I len
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bytes of
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.I src
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into
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.I dst
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without modifying
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.IR src .
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.PP
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.I Salsa_setblock
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sets the Salsa block counter for the next encryption to
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.IR blockno ,
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allowing seeking in an encrypted stream.
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.PP
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.I Salsa_setiv
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sets the the initialization vector (nonce) to
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.IR iv .
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.PP
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.I Hsalsa
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is a key expansion function that takes a 128 or
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256-bit key and a 128-bit nonce and produces a new
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256-bit key.
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.SH SOURCE
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.B /sys/src/libsec/port/salsa.c
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.SH SEE ALSO
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.IR chacha (2)
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.br
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.B http://cr.yp.to/snuffle.html#specification
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