/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*      Copyright (c) 1988 AT&T */
/*        All Rights Reserved   */


/*
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*LINTLIBRARY*/

#include <sys/types.h>

void
_des_decrypt1(char *block, char *L, char *IP, char *R, char *preS, char *E, char KS[][48], char S[][64], char *f, char *tempL, char *P, char *FP)
{
        int     i, ii;
        int     t, j, k;
        char    t2;

        /*
         * First, permute the bits in the input
         */
        for (j = 0; j < 64; j++)
                L[j] = block[IP[j]-1];
        /*
         * Perform a decryption operation 16 times.
         */
        for (ii = 0; ii < 16; ii++) {
                i = 15-ii;
                /*
                 * Save the R array,
                 * which will be the new L.
                 */
                for (j = 0; j < 32; j++)
                        tempL[j] = R[j];
                /*
                 * Expand R to 48 bits using the E selector;
                 * exclusive-or with the current key bits.
                 */
                for (j = 0; j < 48; j++)
                        preS[j] = R[E[j]-1] ^ KS[i][j];
                /*
                 * The pre-select bits are now considered
                 * in 8 groups of 6 bits each.
                 * The 8 selection functions map these
                 * 6-bit quantities into 4-bit quantities
                 * and the results permuted
                 * to make an f(R, K).
                 * The indexing into the selection functions
                 * is peculiar; it could be simplified by
                 * rewriting the tables.
                 */
                for (j = 0; j < 8; j++) {
                        t = 6*j;
                        k = S[j][(preS[t+0]<<5)+
                                (preS[t+1]<<3)+
                                (preS[t+2]<<2)+
                                (preS[t+3]<<1)+
                                (preS[t+4]<<0)+
                                (preS[t+5]<<4)];
                        t = 4*j;
                        f[t+0] = (k>>3)&01;
                        f[t+1] = (k>>2)&01;
                        f[t+2] = (k>>1)&01;
                        f[t+3] = (k>>0)&01;
                }
                /*
                 * The new R is L ^ f(R, K).
                 * The f here has to be permuted first, though.
                 */
                for (j = 0; j < 32; j++)
                        R[j] = L[j] ^ f[P[j]-1];
                /*
                 * Finally, the new L (the original R)
                 * is copied back.
                 */
                for (j = 0; j < 32; j++)
                        L[j] = tempL[j];
        }
        /*
         * The output L and R are reversed.
         */
        for (j = 0; j < 32; j++) {
                t2 = L[j];
                L[j] = R[j];
                R[j] = t2;
        }
        /*
         * The final output
         * gets the inverse permutation of the very original.
         */
        for (j = 0; j < 64; j++)
                block[j] = L[FP[j]-1];
}