diff options
Diffstat (limited to 'g10/seskey.c')
| -rw-r--r-- | g10/seskey.c | 41 |
1 files changed, 40 insertions, 1 deletions
diff --git a/g10/seskey.c b/g10/seskey.c index d81697296..317623ec8 100644 --- a/g10/seskey.c +++ b/g10/seskey.c @@ -1,4 +1,4 @@ -/* seskey.c - make sesssion keys +/* seskey.c - make sesssion keys etc. * Copyright (c) 1997 by Werner Koch (dd9jn) * * This file is part of G10. @@ -99,3 +99,42 @@ encode_session_key( DEK *dek, unsigned nbits ) return frame; } +/**************** + * Encode a ripemd160 message digest of LEN bytes into NBITS. + * returns: A mpi with the session key (caller must free) + */ +MPI +encode_rmd160_value( byte *md, unsigned len, unsigned nbits ) +{ + static byte asn[18] = /* stored reverse FIXME: need other values*/ + { 0x30, 0x20, 0x30, 0x0c, 0x06, 0x08, 0x2a, 0x86,0x48, + 0x86, 0xf7, 0x0d, 0x02, 0x05, 0x05, 0x00, 0x04, 0x10 }; + int nframe = (nbits+7) / 8; + byte *p; + MPI frame; + int i,n,c; + + if( (nbits % BITS_PER_MPI_LIMB) || nframe < 42 || len != 20 ) + log_bug("can't encode a %d bit MD into a %d bits frame\n",len*8, nbits); + + /* We encode the MD in this way: + * + * 0 42 PAD(n bytes) 0 ASN(18 bytes) MD(20 bytes) + * + * PAD consists of FF bytes. + */ + frame = mpi_alloc_secure( nframe / BYTES_PER_MPI_LIMB ); + n = 0; + for(i=20-1; i >= 0; i--, n++ ) + mpi_putbyte(frame, n, md[i] ); + for( i=18-1; i >= 0; i--, n++ ) + mpi_putbyte(frame, n, asn[i] ); + mpi_putbyte(frame, n++, 0 ); + while( n < nframe-2 ) + mpi_putbyte(frame, n++, 0xff ); + mpi_putbyte(frame, n++, DIGEST_ALGO_RMD160 ); + mpi_putbyte(frame, n++, 0 ); + assert( n == nframe ); + return frame; +} + |