Added the arcfour cipher which is of use for GNUTLS.

According to the selftest, it does not yet work :-((.

cipher/arcfour.c

@@ -0,0 +1,165 @@
+/* arcfour.c  -  The arcfour stream cipher
+ *	Copyright (C) 2000 Free Software Foundation, Inc.
+ *
+ * For a description of the algorithm, see:
+ *   Bruce Schneier: Applied Cryptography. John Wiley & Sons, 1996.
+ *   ISBN 0-471-11709-9. Pages 397 ff.
+ *
+ * This file is part of GnuPG.
+ *
+ * GnuPG is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * GnuPG is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ */
+
+
+#include <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "types.h"
+#include "g10lib.h"
+#include "arcfour.h"
+
+static const char *selftest(void);
+
+
+typedef struct {
+    int idx_i, idx_j;
+    byte sbox[256];
+} ARCFOUR_context;
+
+
+static void
+encrypt_stream( ARCFOUR_context *ctx,
+                byte *outbuf, const byte *inbuf, unsigned int length )
+{
+    int t;  
+    int i = ctx->idx_i;
+    int j = ctx->idx_j;
+    byte *sbox = ctx->sbox;
+
+    while ( length-- ) {
+        i = (i+1) % 256;
+        j = (j + sbox[i]) % 256;
+        t = sbox[i]; sbox[i] = sbox[j]; sbox[j] = t;
+        *outbuf++ = *inbuf++ ^ sbox[(sbox[i] + sbox[j]) % 256];
+    }
+
+    ctx->idx_i = i;
+    ctx->idx_j = j;
+}
+
+
+static int
+arcfour_setkey( ARCFOUR_context *ctx, const byte *key, unsigned int keylen )
+{
+    static int initialized;
+    static const char* selftest_failed;
+    int i, j;
+    byte karr[256];
+
+    if( !initialized ) {
+	initialized = 1;
+	selftest_failed = selftest();
+	if( selftest_failed )
+	    fprintf(stderr,"ARCFOUR selftest failed (%s)\n", selftest_failed );
+    }
+    if( selftest_failed )
+	return GCRYERR_SELFTEST;
+
+    if( keylen < 40 )
+	return GCRYERR_INV_KEYLEN;
+
+    ctx->idx_i = ctx->idx_j = 0;
+    for (i=0; i < 256; i++ )
+        ctx->sbox[i] = i;
+    for (i=0; i < 256; i++ )
+        karr[i] = key[i%keylen];
+    for (i=j=0; i < 256; i++ ) {
+        int t;
+        j = (j + ctx->sbox[i] + karr[i]) % 256;
+        t = ctx->sbox[i];
+        ctx->sbox[i] = ctx->sbox[j];
+        ctx->sbox[j] = t;
+    } 
+    memset( karr, 0, 256 );
+
+    return 0;
+}
+
+
+static const char*
+selftest(void)
+{
+    ARCFOUR_context ctx;
+    byte scratch[16];	   
+    
+    /* Test vector from Cryptlib labeled there:
+     * "from the State/Commerce Department" */
+    static const byte key_1[] =
+        { 0x61, 0x8A, 0x63, 0xD2, 0xFB };
+    static const byte plaintext_1[] =
+        { 0xDC, 0xEE, 0x4C, 0xF9, 0x2C };
+    static const byte ciphertext_1[] =
+        { 0xF1, 0x38, 0x29, 0xC9, 0xDE };
+
+    arcfour_setkey( &ctx, key_1, sizeof(key_1));
+    encrypt_stream( &ctx, scratch, plaintext_1, sizeof(plaintext_1));
+    if (memcmp (scratch, ciphertext_1, sizeof (ciphertext_1)))
+        return "Arcfour encryption test 1 failed.";
+    encrypt_stream(&ctx, scratch, scratch, sizeof(plaintext_1)); /* decrypt */
+    if ( memcmp (scratch, plaintext_1, sizeof (plaintext_1)))
+        return "Arcfour decryption test 1 failed.";
+    return NULL;
+}
+
+
+/****************
+ * Return some information about the algorithm.  We need algo here to
+ * distinguish different flavors of the algorithm.
+ * Returns: A pointer to string describing the algorithm or NULL if
+ *	    the ALGO is invalid.
+ * NOTE: This is a special get_info function which is different from all
+ * others because arcfour is a stream cipher.  We use this hack until
+ * we have redesign the interface.
+ */
+const char *
+arcfour_get_info( int algo, size_t *keylen, size_t *blocksize,
+		   size_t *contextsize,
+		   int	(**r_setkey)( void *c, byte *key, unsigned keylen ),
+		   void (**r_stencrypt)( void *c, byte *outbuf,
+                                       byte *inbuf, unsigned int nbytes ),
+		   void (**r_stdecrypt)( void *c, byte *outbuf,
+                                       byte *inbuf, unsigned int nbytes )
+		 )
+{
+    *keylen = 128; /* arbitrary value */
+    *blocksize = 1;
+    *contextsize = sizeof(ARCFOUR_context);
+    *(int  (**)(ARCFOUR_context*, byte*, unsigned))r_setkey
+							= arcfour_setkey;
+    *(void (**)(ARCFOUR_context*, byte*, const byte*, unsigned))r_stencrypt
+							= encrypt_stream;
+    *(void (**)(ARCFOUR_context*, byte*, const byte*, unsigned))r_stdecrypt
+							= encrypt_stream;
+
+
+    if( algo == 301 )
+	return "ARCFOUR";
+    return NULL;
+}
+
+
+
+

cipher/arcfour.h

@@ -0,0 +1,41 @@
+/* arcfour.h
+ *	Copyright (C) 2000 Free Software Foundation, Inc.
+ *
+ * This file is part of GnuPG.
+ *
+ * GnuPG is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * GnuPG is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ */
+#ifndef G10_ARCFOUR_H
+#define G10_ARCFOUR_H
+
+#include "types.h"
+
+/* NOTE: This is a special get_info function which is different from all
+ * others because arcfour is a stream cipher.  We use this hack until
+ * we have redesigned the interface.
+ */
+const char *
+arcfour_get_info( int algo, size_t *keylen, size_t *blocksize,
+		   size_t *contextsize,
+		   int	(**r_setkey)( void *c, byte *key, unsigned keylen ),
+		   void (**r_stencrypt)( void *c, byte *outbuf,
+                                       byte *inbuf, unsigned int nbytes ),
+		   void (**r_stdecrypt)( void *c, byte *outbuf,
+                                       byte *inbuf, unsigned int nbytes )
+                );
+
+
+#endif /*G10_ARCFOUR_H*/
+