ofb_enc.c
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/*
* Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include "des_locl.h"
/*
* The input and output are loaded in multiples of 8 bits. What this means is
* that if you have numbits=12 and length=2 the first 12 bits will be
* retrieved from the first byte and half the second. The second 12 bits
* will come from the 3rd and half the 4th byte.
*/
void DES_ofb_encrypt(const unsigned char *in, unsigned char *out, int numbits,
long length, DES_key_schedule *schedule,
DES_cblock *ivec)
{
register DES_LONG d0, d1, vv0, vv1, v0, v1, n = (numbits + 7) / 8;
register DES_LONG mask0, mask1;
register long l = length;
register int num = numbits;
DES_LONG ti[2];
unsigned char *iv;
if (num > 64)
return;
if (num > 32) {
mask0 = 0xffffffffL;
if (num >= 64)
mask1 = mask0;
else
mask1 = (1L << (num - 32)) - 1;
} else {
if (num == 32)
mask0 = 0xffffffffL;
else
mask0 = (1L << num) - 1;
mask1 = 0x00000000L;
}
iv = &(*ivec)[0];
c2l(iv, v0);
c2l(iv, v1);
ti[0] = v0;
ti[1] = v1;
while (l-- > 0) {
ti[0] = v0;
ti[1] = v1;
DES_encrypt1((DES_LONG *)ti, schedule, DES_ENCRYPT);
vv0 = ti[0];
vv1 = ti[1];
c2ln(in, d0, d1, n);
in += n;
d0 = (d0 ^ vv0) & mask0;
d1 = (d1 ^ vv1) & mask1;
l2cn(d0, d1, out, n);
out += n;
if (num == 32) {
v0 = v1;
v1 = vv0;
} else if (num == 64) {
v0 = vv0;
v1 = vv1;
} else if (num > 32) { /* && num != 64 */
v0 = ((v1 >> (num - 32)) | (vv0 << (64 - num))) & 0xffffffffL;
v1 = ((vv0 >> (num - 32)) | (vv1 << (64 - num))) & 0xffffffffL;
} else { /* num < 32 */
v0 = ((v0 >> num) | (v1 << (32 - num))) & 0xffffffffL;
v1 = ((v1 >> num) | (vv0 << (32 - num))) & 0xffffffffL;
}
}
iv = &(*ivec)[0];
l2c(v0, iv);
l2c(v1, iv);
v0 = v1 = d0 = d1 = ti[0] = ti[1] = vv0 = vv1 = 0;
}