A local copy of OpenSSL from GitHub
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/*
* Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (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
*/
/*
* DES low level APIs are deprecated for public use, but still ok for internal
* use.
*/
#include "internal/deprecated.h"
#include "des_local.h"
/*
* The input and output encrypted as though 64bit cfb mode is being used.
* The extra state information to record how much of the 64bit block we have
* used is contained in *num;
*/
void DES_cfb64_encrypt(const unsigned char *in, unsigned char *out,
long length, DES_key_schedule *schedule,
DES_cblock *ivec, int *num, int enc)
{
register DES_LONG v0, v1;
register long l = length;
register int n = *num;
DES_LONG ti[2];
unsigned char *iv, c, cc;
iv = &(*ivec)[0];
if (enc) {
while (l--) {
if (n == 0) {
c2l(iv, v0);
ti[0] = v0;
c2l(iv, v1);
ti[1] = v1;
DES_encrypt1(ti, schedule, DES_ENCRYPT);
iv = &(*ivec)[0];
v0 = ti[0];
l2c(v0, iv);
v0 = ti[1];
l2c(v0, iv);
iv = &(*ivec)[0];
}
c = *(in++) ^ iv[n];
*(out++) = c;
iv[n] = c;
n = (n + 1) & 0x07;
}
} else {
while (l--) {
if (n == 0) {
c2l(iv, v0);
ti[0] = v0;
c2l(iv, v1);
ti[1] = v1;
DES_encrypt1(ti, schedule, DES_ENCRYPT);
iv = &(*ivec)[0];
v0 = ti[0];
l2c(v0, iv);
v0 = ti[1];
l2c(v0, iv);
iv = &(*ivec)[0];
}
cc = *(in++);
c = iv[n];
iv[n] = cc;
*(out++) = c ^ cc;
n = (n + 1) & 0x07;
}
}
v0 = v1 = ti[0] = ti[1] = c = cc = 0;
*num = n;
}