SALSA(2)                                                 SALSA(2)

     NAME
          setupSalsastate, salsa_setblock, salsa_setiv, salsa_encrypt,
          salsa_encrypt2, hsalsa - salsa20 encryption

     SYNOPSIS
          #include <u.h>
          #include <libc.h>
          #include <libsec.h>

          void setupSalsastate(Salsastate *s, uchar key[], ulong
          keylen, uchar *iv, ulong ivlen, int rounds)

          void salsa_encrypt(uchar *data, ulong len, Salsastate *s)

          void salsa_encrypt2(uchar *src, uchar *dst, ulong len, Sal-
          sastate *s)

          void salsa_setblock(Salsastate *s, u64int blockno)

          void salsa_setiv(Salsastate *s, uchar *iv);

          void hsalsa(uchar h[32], uchar *key, ulong keylen, uchar
          nonce[16], int rounds);

     DESCRIPTION
          Salsa20 is a stream cipher designed by D J Berstein. It has
          an underlying block size of 64 bytes (named as constant
          SalsaBsize).  It supports key sizes of 128 and 256-bit (rec-
          ommended).

          SetupSalsastate takes a reference to a Salsastate structure,
          a key of keylen bytes, which should normally be
          SalsaKeylen=32, a iv or nonce of ivlen bytes (can be
          SalsaIVlen=8 or XSalsaIVlen=24, set to all zeros if the iv
          argument is nil), and the number of rounds (set to the
          default of 20 if the argument is zero).

          Salsa_encrypt encrypts len bytes of buf in place using the
          Salsastate in s. Len can be any byte length.  Encryption and
          decryption are the same operation given the same starting
          state s.

          Salsa_encrypt2 is similar, but encrypts len bytes of src
          into dst without modifying src.

          Salsa_setblock sets the Salsa block counter for the next
          encryption to blockno, allowing seeking in an encrypted
          stream.

          Salsa_setiv sets the the initialization vector (nonce) to

     SALSA(2)                                                 SALSA(2)

          iv.

          Hsalsa is a key expansion function that takes a 128 or 256-
          bit key and a 128-bit nonce and produces a new 256-bit key.

     SOURCE
          /sys/src/libsec/port/salsa.c

     SEE ALSO
          chacha(2)
          http://cr.yp.to/snuffle.html#specification