openssl/crypto/idea/i_skey.c

/*
 * 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
 */

/*
 * IDEA low level APIs are deprecated for public use, but still ok for internal
 * use where we're using them to implement the higher level EVP interface, as is
 * the case here.
 */
#include "internal/deprecated.h"

#include <openssl/idea.h>
#include "idea_local.h"

static IDEA_INT inverse(unsigned int xin);
void IDEA_set_encrypt_key(const unsigned char *key, IDEA_KEY_SCHEDULE *ks)
{
    int i;
    register IDEA_INT *kt, *kf, r0, r1, r2;

    kt = &(ks->data[0][0]);
    n2s(key, kt[0]);
    n2s(key, kt[1]);
    n2s(key, kt[2]);
    n2s(key, kt[3]);
    n2s(key, kt[4]);
    n2s(key, kt[5]);
    n2s(key, kt[6]);
    n2s(key, kt[7]);

    kf = kt;
    kt += 8;
    for (i = 0; i < 6; i++) {
        r2 = kf[1];
        r1 = kf[2];
        *(kt++) = ((r2 << 9) | (r1 >> 7)) & 0xffff;
        r0 = kf[3];
        *(kt++) = ((r1 << 9) | (r0 >> 7)) & 0xffff;
        r1 = kf[4];
        *(kt++) = ((r0 << 9) | (r1 >> 7)) & 0xffff;
        r0 = kf[5];
        *(kt++) = ((r1 << 9) | (r0 >> 7)) & 0xffff;
        r1 = kf[6];
        *(kt++) = ((r0 << 9) | (r1 >> 7)) & 0xffff;
        r0 = kf[7];
        *(kt++) = ((r1 << 9) | (r0 >> 7)) & 0xffff;
        r1 = kf[0];
        if (i >= 5)
            break;
        *(kt++) = ((r0 << 9) | (r1 >> 7)) & 0xffff;
        *(kt++) = ((r1 << 9) | (r2 >> 7)) & 0xffff;
        kf += 8;
    }
}

void IDEA_set_decrypt_key(IDEA_KEY_SCHEDULE *ek, IDEA_KEY_SCHEDULE *dk)
{
    int r;
    register IDEA_INT *fp, *tp, t;

    tp = &(dk->data[0][0]);
    fp = &(ek->data[8][0]);
    for (r = 0; r < 9; r++) {
        *(tp++) = inverse(fp[0]);
        *(tp++) = ((int)(0x10000L - fp[2]) & 0xffff);
        *(tp++) = ((int)(0x10000L - fp[1]) & 0xffff);
        *(tp++) = inverse(fp[3]);
        if (r == 8)
            break;
        fp -= 6;
        *(tp++) = fp[4];
        *(tp++) = fp[5];
    }

    tp = &(dk->data[0][0]);
    t = tp[1];
    tp[1] = tp[2];
    tp[2] = t;

    t = tp[49];
    tp[49] = tp[50];
    tp[50] = t;
}

/* taken directly from the 'paper' I'll have a look at it later */
static IDEA_INT inverse(unsigned int xin)
{
    long n1, n2, q, r, b1, b2, t;

    if (xin == 0)
        b2 = 0;
    else {
        n1 = 0x10001;
        n2 = xin;
        b2 = 1;
        b1 = 0;

        do {
            r = (n1 % n2);
            q = (n1 - r) / n2;
            if (r == 0) {
                if (b2 < 0)
                    b2 = 0x10001 + b2;
            } else {
                n1 = n2;
                n2 = r;
                t = b2;
                b2 = b1 - q * b2;
                b1 = t;
            }
        } while (r != 0);
    }
    return (IDEA_INT)b2;
}