267 lines
5.8 KiB
C
267 lines
5.8 KiB
C
/*
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* File: cast6.c
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* Author: Daniel Otte
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* Date: 09.09.2006
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* License: GPL
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* Description: Implementation of the CAST6 (aka CAST-256) cipher algorithm as described in RFC 2612
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*
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*/
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#include <stdint.h>
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#include <string.h>
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#include "cast6.h"
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#include "cast6_sboxes.h"
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#define CHANGE_ENDIAN32(x) (((x)<<24 | (x)>>24 | ((x)&0xff00)<<8 | ((x)&0xff0000)>>8)&0xffffffff)
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static
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uint8_t kr(uint8_t i, const cast6_ctx_t* ctx){
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uint8_t ret;
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ret = ctx->krx[i/2];
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if(i&1){
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ret >>= 4;
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}else{
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ret &= 0x0f;
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}
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/* now get the high bit */
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ret |= ((ctx->krx[24+i/8])&(1<<(i%8)))?0x10:0x00;
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return ret;
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}
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static
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void set_kr(uint8_t value, uint8_t i, cast6_ctx_t* ctx){
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value &= 0x1F;
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(ctx->krx[i/2]) &= 0xF0>>((i&1)*4); /* clear the location where v should go */
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(ctx->krx[i/2]) |= (value&0x0f)<<((i&1)*4);
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/* now set the high bit */
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(ctx->krx[24+i/8]) &= ~(1<<(i%8)); /* clear the location where v should go */
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(ctx->krx[24+i/8]) |= (value>>4)<<(i%8);
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}
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#define ROTL32(a,n) (((a)<<(n))|((a)>>(32-(n))))
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#define ROTR32(a,n) (((a)>>(n))|((a)<<(32-(n))))
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#define S1(a) (s1[(a)])
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#define S2(a) (s2[(a)])
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#define S3(a) (s3[(a)])
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#define S4(a) (s4[(a)])
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#define A ((uint8_t)(v>>(8*3)))
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#define B ((uint8_t)(v>>(8*2)))
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#define C ((uint8_t)(v>>(8*1)))
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#define D ((uint8_t)(v>>(8*0)))
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static
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uint32_t f1(uint32_t v, uint8_t kri, uint32_t kmi){
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uint32_t o;
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kri &= 0x1F;
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v = ROTL32(kmi+v, kri);
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o = S1(A);
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o ^= S2(B);
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o -= S3(C);
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o += S4(D);
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return o;
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}
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static
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uint32_t f2(uint32_t v, uint8_t kri, uint32_t kmi){
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uint32_t o;
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kri &= 0x1F;
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v = ROTL32(kmi^v, kri);
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o = S1(A);
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o -= S2(B);
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o += S3(C);
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o ^= S4(D);
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return o;
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}
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static
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uint32_t f3(uint32_t v, uint8_t kri, uint32_t kmi){
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uint32_t o;
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kri &= 0x1F;
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v = ROTL32(kmi-v, kri);
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o = S1(A);
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o += S2(B);
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o ^= S3(C);
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o -= S4(D);
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return o;
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}
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#undef A
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#undef B
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#undef C
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#undef D
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#define A (((uint32_t*)buffer)[0])
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#define B (((uint32_t*)buffer)[1])
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#define C (((uint32_t*)buffer)[2])
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#define D (((uint32_t*)buffer)[3])
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static
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void q(void* buffer, uint8_t i, const cast6_ctx_t* ctx){
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C ^= f1(D, kr(i*4+0, ctx), ctx->km[i][0]);
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B ^= f2(C, kr(i*4+1, ctx), ctx->km[i][1]);
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A ^= f3(B, kr(i*4+2, ctx), ctx->km[i][2]);
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D ^= f1(A, kr(i*4+3, ctx), ctx->km[i][3]);
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}
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static
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void qbar(void* buffer, uint8_t i, const cast6_ctx_t* ctx){
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D ^= f1(A, kr(i*4+3, ctx), ctx->km[i][3]);
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A ^= f3(B, kr(i*4+2, ctx), ctx->km[i][2]);
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B ^= f2(C, kr(i*4+1, ctx), ctx->km[i][1]);
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C ^= f1(D, kr(i*4+0, ctx), ctx->km[i][0]);
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}
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void cast6_enc(void* buffer, const cast6_ctx_t* ctx){
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uint8_t i;
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for(i=0; i<32/4; ++i){
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((uint32_t*)buffer)[i] = CHANGE_ENDIAN32(((uint32_t*)buffer)[i]);
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}
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for(i=0; i<6; ++i){
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q(buffer, i, ctx);
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}
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for(i=6; i<12; ++i){
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qbar(buffer, i, ctx);
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}
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for(i=0; i<32/4; ++i){
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((uint32_t*)buffer)[i] = CHANGE_ENDIAN32(((uint32_t*)buffer)[i]);
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}
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}
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void cast6_dec(void* buffer, const cast6_ctx_t* ctx){
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uint8_t i;
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for(i=0; i<32/4; ++i){
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((uint32_t*)buffer)[i] = CHANGE_ENDIAN32(((uint32_t*)buffer)[i]);
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}
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for(i=12; i>6; --i){
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q(buffer, i-1, ctx);
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}
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for(i=6; i>0; --i){
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qbar(buffer, i-1, ctx);
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}
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for(i=0; i<32/4; ++i){
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((uint32_t*)buffer)[i] = CHANGE_ENDIAN32(((uint32_t*)buffer)[i]);
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}
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}
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#undef A
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#undef B
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#undef C
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#undef D
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#define A (((uint32_t*)buffer)[0])
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#define B (((uint32_t*)buffer)[1])
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#define C (((uint32_t*)buffer)[2])
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#define D (((uint32_t*)buffer)[3])
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#define E (((uint32_t*)buffer)[4])
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#define F (((uint32_t*)buffer)[5])
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#define G (((uint32_t*)buffer)[6])
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#define H (((uint32_t*)buffer)[7])
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/*
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* we might later make it optional to use this small thing
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static
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void w(void* buffer, uint8_t* tr, uint32_t* tm){
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G ^= f1(H, (tr[0]&0x0f)+(tr[5]&0x01)?0x10:0x00, tm[0]);
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F ^= f2(G, (tr[0]>>4) +(tr[5]&0x02)?0x10:0x00, tm[1]);
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E ^= f3(F, (tr[1]&0x0f)+(tr[5]&0x04)?0x10:0x00, tm[2]);
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D ^= f1(E, (tr[1]>>4) +(tr[5]&0x08)?0x10:0x00, tm[3]);
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C ^= f2(D, (tr[2]&0x0f)+(tr[5]&0x10)?0x10:0x00, tm[4]);
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B ^= f3(C, (tr[2]>>4) +(tr[5]&0x20)?0x10:0x00, tm[5]);
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A ^= f1(B, (tr[3]&0x0f)+(tr[5]&0x40)?0x10:0x00, tm[6]);
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H ^= f2(A, (tr[3]>>4) +(tr[5]&0x80)?0x10:0x00, tm[7]);
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}
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*/
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static
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void w(void* buffer, uint8_t* tr, uint32_t* tm){
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G ^= f1(H, tr[0], tm[0]);
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F ^= f2(G, tr[1], tm[1]);
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E ^= f3(F, tr[2], tm[2]);
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D ^= f1(E, tr[3], tm[3]);
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C ^= f2(D, tr[4], tm[4]);
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B ^= f3(C, tr[5], tm[5]);
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A ^= f1(B, tr[6], tm[6]);
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H ^= f2(A, tr[7], tm[7]);
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}
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/*
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void dump_ctx(const cast6_ctx_t* ctx){
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uint8_t i,t;
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cli_putstr("\r\n DBG:");
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for(i=0; i<12; ++i){
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cli_putstr("\r\n DBG:");
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cli_putstr(" rotk1=");
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t=kr(i*4+0, ctx);
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cli_hexdump(&t,1);
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cli_putstr(" rotk2=");
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t=kr(i*4+1, ctx);
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cli_hexdump(&t,1);
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cli_putstr(" rotk3=");
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t=kr(i*4+2, ctx);
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cli_hexdump(&t,1);
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cli_putstr(" rotk4=");
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t=kr(i*4+3, ctx);
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cli_hexdump(&t,1);
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cli_putstr("\r\n ");
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cli_putstr(" mask1=");
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cli_hexdump(&(ctx->km[i][0]),4);
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cli_putstr(" mask2=");
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cli_hexdump(&(ctx->km[i][1]),4);
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cli_putstr(" mask3=");
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cli_hexdump(&(ctx->km[i][2]),4);
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cli_putstr(" mask4=");
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cli_hexdump(&(ctx->km[i][3]),4);
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cli_putstr("\r\n;-----");
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}
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}
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*/
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#define CR 19
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#define CM 0x5A827999
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#define MR 17
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#define MM 0x6ED9EBA1
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void cast6_init(const void* key, uint16_t keysize_b, cast6_ctx_t* ctx){
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uint8_t buffer[32];
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uint8_t cr=CR, tr[8];
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uint32_t cm=CM, tm[8];
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uint8_t i,j;
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memset(buffer, 0, 32);
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memcpy(buffer, key, (keysize_b+7)/8);
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for(i=0; i<32/4; ++i){
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((uint32_t*)buffer)[i] = CHANGE_ENDIAN32(((uint32_t*)buffer)[i]);
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}
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for(i=0; i<24; ++i){
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for(j=0; j<8; ++j){
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tm[j] = cm;
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cm += MM;
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tr[j] = cr&0x1F;
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cr += MR;
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}
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w(buffer, tr, tm);
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if(i&1){
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j=i/2;
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ctx->km[j][0]=H;
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ctx->km[j][1]=F;
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ctx->km[j][2]=D;
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ctx->km[j][3]=B;
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set_kr(buffer[0 * 4],j*4+0,ctx);
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set_kr(buffer[2 * 4],j*4+1,ctx);
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set_kr(buffer[4 * 4],j*4+2,ctx);
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set_kr(buffer[6 * 4],j*4+3,ctx);
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}
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}
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}
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