openssl/crypto/cast/c_ofb64.c

/*
 * Copyright 1995-2016 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
 */

#include <openssl/cast.h>
#include "cast_lcl.h"

/*
 * The input and output encrypted as though 64bit ofb mode is being used.
 * The extra state information to record how much of the 64bit block we have
 * used is contained in *num;
 */
void CAST_ofb64_encrypt(const unsigned char *in, unsigned char *out,
                        long length, const CAST_KEY *schedule,
                        unsigned char *ivec, int *num)
{
    register CAST_LONG v0, v1, t;
    register int n = *num;
    register long l = length;
    unsigned char d[8];
    register char *dp;
    CAST_LONG ti[2];
    unsigned char *iv;
    int save = 0;

    iv = ivec;
    n2l(iv, v0);
    n2l(iv, v1);
    ti[0] = v0;
    ti[1] = v1;
    dp = (char *)d;
    l2n(v0, dp);
    l2n(v1, dp);
    while (l--) {
        if (n == 0) {
            CAST_encrypt((CAST_LONG *)ti, schedule);
            dp = (char *)d;
            t = ti[0];
            l2n(t, dp);
            t = ti[1];
            l2n(t, dp);
            save++;
        }
        *(out++) = *(in++) ^ d[n];
        n = (n + 1) & 0x07;
    }
    if (save) {
        v0 = ti[0];
        v1 = ti[1];
        iv = ivec;
        l2n(v0, iv);
        l2n(v1, iv);
    }
    t = v0 = v1 = ti[0] = ti[1] = 0;
    *num = n;
}