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twenty4.c
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308
twenty4.c
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/*
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******* THIS IS JUST FOR LEARINING CRYPTO, DO NOT EVER USE THIS FOR ANYTHING *******
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This is the implementation of the fun stream cipher TWENTY4 by Thomas von Dein, 09/2015.
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Published under the public domain, Creative Commons Zero License.
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*/
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#include <stdio.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <string.h>
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#include <ctype.h>
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#include <math.h>
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typedef uint8_t byte;
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typedef uint32_t word;
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typedef uint16_t half;
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const byte kbox[] = {
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0x53, 0x61, 0x6c, 0x74, 0x65, 0x64, 0x5f, 0xdf, 0x40, 0xc1, 0x9d, 0x46, 0x33, 0x45, 0x92, 0x95,
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0xd8, 0x24, 0xf5, 0x1c, 0xe0, 0x29, 0xff, 0xa3, 0x71, 0x6f, 0x35, 0x2e, 0x4b, 0x0d, 0xa7, 0x5d,
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0x97, 0xe1, 0x98, 0x58, 0x2b, 0xc4, 0xae, 0xe3, 0xec, 0xb8, 0x38, 0xee, 0x91, 0x2c, 0xb4, 0xa0,
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0xc6, 0x34, 0x1f, 0x57, 0x0e, 0xc3, 0x4f, 0xb9, 0x80, 0x21, 0x5b, 0x06, 0xf6, 0x87, 0xfa, 0x5e,
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0xe7, 0xda, 0xce, 0xdd, 0x23, 0xe9, 0x03, 0x39, 0xa5, 0x8e, 0xb6, 0xca, 0x3c, 0x7a, 0x44, 0x2d,
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0x07, 0xcf, 0x1b, 0xd0, 0x94, 0x85, 0xc5, 0x20, 0xaa, 0x81, 0xc9, 0xb7, 0x2f, 0xfb, 0xb2, 0x50,
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0x54, 0xf0, 0x14, 0xd9, 0x00, 0x67, 0x15, 0x9f, 0xa2, 0x02, 0x93, 0xcc, 0xdb, 0x8d, 0x30, 0x78,
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0xb1, 0x7b, 0x19, 0xc0, 0x43, 0x6b, 0xbb, 0x2a, 0x3b, 0x4d, 0xe4, 0x08, 0x12, 0x90, 0x32, 0xef,
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0xe8, 0x5a, 0xac, 0xf4, 0x8c, 0xe2, 0x4e, 0x6d, 0xaf, 0x66, 0xf8, 0xbc, 0x36, 0x72, 0x01, 0x1e,
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0x68, 0x37, 0x59, 0x51, 0xa6, 0x7c, 0xbe, 0x86, 0x8a, 0x8b, 0xfe, 0x0a, 0x05, 0x52, 0x76, 0x27,
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0x69, 0x18, 0x22, 0x63, 0x42, 0x4a, 0xad, 0x10, 0xe5, 0xa1, 0xc8, 0xeb, 0xb0, 0x09, 0x6a, 0x4c,
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0x16, 0xf7, 0xde, 0xfc, 0x7f, 0x7d, 0xdc, 0x99, 0xbd, 0x7e, 0x26, 0xcd, 0xba, 0xc2, 0xa8, 0x04,
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0x0f, 0x3e, 0x82, 0x1d, 0x89, 0xb5, 0x31, 0xb3, 0x47, 0x6e, 0xf3, 0x0b, 0xd3, 0x84, 0x49, 0x0c,
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0x3d, 0xd5, 0x9a, 0xd6, 0x9e, 0xd7, 0x8f, 0xa9, 0x79, 0xd4, 0x48, 0x9b, 0x55, 0x56, 0xcb, 0x3a,
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0xf9, 0xfd, 0xd2, 0xe6, 0x75, 0x1a, 0x11, 0xf2, 0xa4, 0x5c, 0x96, 0x13, 0xea, 0xd1, 0xbf, 0x60,
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0x28, 0xab, 0x9c, 0x77, 0x83, 0x62, 0x17, 0x41, 0x70, 0x25, 0xf1, 0x3f, 0x88, 0x73, 0xc7, 0xed,
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};
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const byte sbox[] = {
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0x61, 0x2d, 0x19, 0xf3, 0xe5, 0xd9, 0xde, 0x5f, 0x41, 0x31, 0xa7, 0xc2, 0x48, 0x02, 0xef, 0x98,
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0x67, 0xcb, 0x6e, 0x4c, 0xf4, 0x11, 0xfa, 0x87, 0x0f, 0x6f, 0x0a, 0x3b, 0x71, 0x09, 0x1a, 0xb8,
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0x3c, 0x44, 0xd8, 0xd4, 0xc8, 0x91, 0x6d, 0x8c, 0x2f, 0xce, 0x85, 0x22, 0xd5, 0x08, 0xa6, 0x97,
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0x68, 0xbc, 0x3a, 0xa0, 0xbf, 0xa5, 0x47, 0x94, 0x83, 0xd1, 0x18, 0x29, 0x03, 0xb2, 0xa4, 0xfe,
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0xe4, 0x4d, 0xdf, 0x21, 0xc0, 0x70, 0x4f, 0x90, 0x04, 0x40, 0x0b, 0x49, 0xe0, 0x25, 0xd7, 0xda,
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0xf8, 0x1f, 0x9e, 0x76, 0xbb, 0xaa, 0xc5, 0x2e, 0x72, 0x64, 0xd6, 0x74, 0x10, 0x78, 0xfd, 0x45,
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0x80, 0x4e, 0x7f, 0x12, 0xb7, 0xc6, 0xea, 0xb3, 0x37, 0x5a, 0xf2, 0xc3, 0xb6, 0x5b, 0x81, 0x95,
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0xbd, 0xb0, 0xae, 0x8f, 0xd2, 0xcf, 0x1e, 0xc7, 0xee, 0xa1, 0x7a, 0xb9, 0x06, 0xa8, 0xb1, 0x93,
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0x30, 0xad, 0x33, 0x77, 0x3d, 0x7c, 0xb4, 0x36, 0x92, 0x15, 0x89, 0x7e, 0xe9, 0x17, 0x07, 0x8a,
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0x9f, 0x32, 0x2c, 0xf9, 0xb5, 0x7d, 0xeb, 0x23, 0xdc, 0x2b, 0x63, 0x88, 0x56, 0x42, 0x84, 0x4b,
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0x0e, 0xec, 0x8d, 0x7b, 0x05, 0xed, 0xca, 0xe8, 0xe6, 0xba, 0x01, 0x5d, 0x26, 0x28, 0x13, 0x9d,
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0x54, 0x59, 0xfb, 0xf0, 0xd3, 0xf7, 0xdb, 0xe7, 0xbe, 0x58, 0x5e, 0x99, 0x65, 0x8b, 0x20, 0xa3,
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0xc1, 0x1c, 0xaf, 0xac, 0x55, 0xe3, 0xdd, 0x62, 0x2a, 0xcc, 0xd0, 0xe2, 0x0c, 0x66, 0x96, 0x8e,
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0xab, 0xfc, 0xc4, 0x1d, 0x6a, 0x6c, 0x3f, 0x9b, 0x9a, 0x51, 0xa2, 0x86, 0x52, 0x4a, 0x43, 0x14,
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0x75, 0xff, 0xf5, 0xcd, 0x1b, 0x0d, 0x35, 0x24, 0x9c, 0xe1, 0x60, 0x73, 0x3e, 0x39, 0x53, 0x16,
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0x50, 0x6b, 0xc9, 0x46, 0x57, 0x5c, 0x69, 0x79, 0x82, 0xf1, 0x27, 0x38, 0x34, 0xf6, 0x00, 0xa9,
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};
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byte revsbox[256];
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#define K_HASH_ROUNDS 32
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#define S_BOX_ROUNDS 17
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byte rot8left(byte in, int rot) {
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return (in >> (8-rot)) | (in << rot);
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}
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byte rot8right(byte in, int rot) {
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return (in << (8-rot)) | (in >> rot);
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}
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void printbits(byte v) {
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int i;
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for(i = 7; i >= 0; i--) fprintf(stderr, "%c", '0' + ((v >> i) & 1));
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}
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void dump8(char *n, byte d) {
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fprintf(stderr, "%s: %02x ", n, d);
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printbits(d);
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fprintf(stderr, "\n");
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}
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void dumpN(char *n, byte *d, size_t s) {
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int l = strlen(n) + 9;
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fprintf(stderr, "%s (%04ld): ", n, s);
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size_t i;
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int c;
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for (i=0; i<s; ++i) {
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fprintf(stderr, "%02x ", d[i]);
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if(i % 8 == 7 && i > 0) {
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fprintf(stderr, "\n");
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for(c=0; c<l; ++c)
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fprintf(stderr, " ");
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}
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}
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fprintf(stderr, "\n");
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}
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/* for decryption */
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void reverse_sbox() {
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int i;
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for(i=0; i<256; i++)
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revsbox[sbox[i]] = i;
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}
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byte getiv() {
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FILE *RAND;
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byte rand;
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if((RAND = fopen("/dev/urandom", "rb")) == NULL) {
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perror("Could not open /dev/urandom");
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exit(1);
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}
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if(fread(&rand, 1, 1, RAND) != 1) {
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perror("Could not read from /dev/urandom");
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exit(1);
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}
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fclose(RAND);
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return rand;
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}
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byte rcon(byte in) {
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byte c=1;
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if(in == 0)
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return 0;
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while(in != 1) {
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byte b;
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b = c & 0x80;
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c <<= 1;
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if(b == 0x80) {
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c ^= 0x1b;
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}
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in--;
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}
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return c;
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}
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/* we use rounds * 8bit sub keys expanded from
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given password */
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void keyhash(char *pw, byte *hash) {
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byte iv;
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int i, round;
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unsigned int HEX;
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size_t pwlen;
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if(strncmp(pw, "0x", 2) == 0) {
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/* hex pw */
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sscanf(pw, "0x%02x", &HEX);
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pw[0] = (byte)HEX;
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pwlen = 1;
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}
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else {
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pwlen = strlen(pw);
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}
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iv = kbox[(byte)pw[0]];
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/* stretch pw */
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for(i=0; i<S_BOX_ROUNDS; i++) {
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if((size_t)i < pwlen)
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hash[i] = iv ^ pw[i];
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else
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hash[i] = iv ^ kbox[i*8];
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hash[i] = kbox[hash[i]];
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iv = hash[i];
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}
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/* diffuse and confuse hash */
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for(round=0; round<K_HASH_ROUNDS; round++) {
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for(i=0; i<S_BOX_ROUNDS; i++) {
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hash[i] = iv ^ (rot8left(hash[i], 3) ^ kbox[rcon(iv)]);
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iv = hash[i];
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}
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}
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}
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void reverse(byte a[], int sz) {
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int i, j;
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for (i = 0, j = sz; i < j; i++, j--) {
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byte tmp = a[i];
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a[i] = a[j];
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a[j] = tmp;
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}
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}
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void rotate(byte array[], int size, int amt) {
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if (amt < 0)
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amt = size + amt;
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reverse(array, size-amt-1);
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reverse(array+size-amt, amt-1);
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reverse(array, size-1);
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}
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void rotatekey(byte *key, byte feedback) {
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rotate(key, S_BOX_ROUNDS, 1);
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int i;
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for(i=0; i<S_BOX_ROUNDS; i++) {
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key[i] = kbox[key[i] ^ feedback];
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}
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}
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/* actual stream cipher:
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- xor with round key
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- apply sbox
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- rotate left by (round mod 8) bits
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- xor with (round key rotated left by 4 bits [halfes reversed])
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*/
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byte bytebox(byte in, byte *key, int encrypt) {
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int i;
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byte out = in;
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if(encrypt) {
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for(i=0; i<S_BOX_ROUNDS; i++) {
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out ^= key[i];
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out = sbox[out];
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out = rot8left(out, i%8);
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out ^= rot8right(key[i], 4);
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}
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rotatekey(key, out);
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}
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else {
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for(i=S_BOX_ROUNDS-1; i>= 0; i--) {
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out ^= rot8left(key[i], 4);
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out = rot8right(out, i%8);
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out = revsbox[out];
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out ^= key[i];
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}
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rotatekey(key, in);
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}
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return out;
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}
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/* work on stdin and stdout */
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int handleio(byte *key, int encrypt) {
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byte in, out;
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while (fread(&in, 1, 1, stdin) == 1) {
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out = bytebox(in, key, encrypt);
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fwrite(&out, 1, 1, stdout);
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}
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return 0;
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}
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/* work on stdin and stdout, in CBC 8bit mode */
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int cbc_handleio(byte *key, int encrypt) {
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byte in, out, iv;
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if(encrypt) {
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iv = getiv();
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fwrite(&iv, 1, 1, stdout);
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}
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else {
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fread(&iv, 1, 1, stdin);
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}
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while (fread(&in, 1, 1, stdin) == 1) {
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if(encrypt) {
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out = bytebox(iv ^ in, key, encrypt);
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iv = out;
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}
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else {
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out = iv ^ bytebox(in, key, encrypt);
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iv = in;
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}
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fwrite(&out, 1, 1, stdout);
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}
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return 0;
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}
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int main(int argc, char **argv) {
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byte key[S_BOX_ROUNDS];
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int encrypt;
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if(argc != 3) {
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fprintf(stderr, "Usage: stream <passwd> <e|n>\ne=encrypt, n=decrypt\n");
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return 1;
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}
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else {
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encrypt = 0;
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if(strcmp(argv[2], "e") == 0)
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encrypt = 1;
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reverse_sbox();
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keyhash(argv[1], key);
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return handleio(key, encrypt);
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}
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}
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