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/*

 * Implementation of the Secure Hashing Algorithm (SHA-256)

 *

 * Generates a 256 bit message digest. It should be impossible to come

 * come up with two messages that hash to the same value ("collision free").

 *

 * For use with byte-oriented messages only. Could/Should be speeded

 * up by unwinding loops in shs_transform(), and assembly patches.

 */

#include <stdio.h>

#include "miracl.h"

#define H0 0x6A09E667L

#define H1 0xBB67AE85L

#define H2 0x3C6EF372L

#define H3 0xA54FF53AL

#define H4 0x510E527FL

#define H5 0x9B05688CL

#define H6 0x1F83D9ABL

#define H7 0x5BE0CD19L

static mr_unsign32 K[64]={

0x428a2f98L,0x71374491L,0xb5c0fbcfL,0xe9b5dba5L,0x3956c25bL,0x59f111f1L,0x923f82a4L,0xab1c5ed5L,

0xd807aa98L,0x12835b01L,0x243185beL,0x550c7dc3L,0x72be5d74L,0x80deb1feL,0x9bdc06a7L,0xc19bf174L,

0xe49b69c1L,0xefbe4786L,0x0fc19dc6L,0x240ca1ccL,0x2de92c6fL,0x4a7484aaL,0x5cb0a9dcL,0x76f988daL,

0x983e5152L,0xa831c66dL,0xb00327c8L,0xbf597fc7L,0xc6e00bf3L,0xd5a79147L,0x06ca6351L,0x14292967L,

0x27b70a85L,0x2e1b2138L,0x4d2c6dfcL,0x53380d13L,0x650a7354L,0x766a0abbL,0x81c2c92eL,0x92722c85L,

0xa2bfe8a1L,0xa81a664bL,0xc24b8b70L,0xc76c51a3L,0xd192e819L,0xd6990624L,0xf40e3585L,0x106aa070L,

0x19a4c116L,0x1e376c08L,0x2748774cL,0x34b0bcb5L,0x391c0cb3L,0x4ed8aa4aL,0x5b9cca4fL,0x682e6ff3L,

0x748f82eeL,0x78a5636fL,0x84c87814L,0x8cc70208L,0x90befffaL,0xa4506cebL,0xbef9a3f7L,0xc67178f2L};

#define PAD  0x80

#define ZERO 0

/* functions */

#define S(n,x) (((x)>>n) | ((x)<<(32-n)))

#define R(n,x) ((x)>>n)

#define Ch(x,y,z)  ((x&y)^(~(x)&z))

#define Maj(x,y,z) ((x&y)^(x&z)^(y&z))

#define Sig0(x)    (S(2,x)^S(13,x)^S(22,x))

#define Sig1(x)    (S(6,x)^S(11,x)^S(25,x))

#define theta0(x)  (S(7,x)^S(18,x)^R(3,x))

#define theta1(x)  (S(17,x)^S(19,x)^R(10,x))

static void shs_transform(sha256 *sh)

{ /* basic transformation step */

    mr_unsign32 a,b,c,d,e,f,g,h,t1,t2;

    int j;

    for (j=16;j<64;j++)

        sh->w[j]=theta1(sh->w[j-2])+sh->w[j-7]+theta0(sh->w[j-15])+sh->w[j-16];

    a=sh->h[0]; b=sh->h[1]; c=sh->h[2]; d=sh->h[3];

    e=sh->h[4]; f=sh->h[5]; g=sh->h[6]; h=sh->h[7];

    for (j=0;j<64;j++)

    { /* 64 times - mush it up */

        t1=h+Sig1(e)+Ch(e,f,g)+K[j]+sh->w[j];

        t2=Sig0(a)+Maj(a,b,c);

        h=g; g=f; f=e;

        e=d+t1;

        d=c;

        c=b;

        b=a;

        a=t1+t2;

    }

    sh->h[0]+=a; sh->h[1]+=b; sh->h[2]+=c; sh->h[3]+=d;

    sh->h[4]+=e; sh->h[5]+=f; sh->h[6]+=g; sh->h[7]+=h;

}

void shs256_init(sha256 *sh)

{ /* re-initialise */

    int i;

    for (i=0;i<64;i++) sh->w[i]=0L;

    sh->length[0]=sh->length[1]=0L;

    sh->h[0]=H0;

    sh->h[1]=H1;

    sh->h[2]=H2;

    sh->h[3]=H3;

    sh->h[4]=H4;

    sh->h[5]=H5;

    sh->h[6]=H6;

    sh->h[7]=H7;

}

void shs256_process(sha256 *sh,int byte)

{ /* process the next message byte */

    int cnt;

    cnt=(int)((sh->length[0]/32)%16);

    sh->w[cnt]<<=8;

    sh->w[cnt]|=(mr_unsign32)(byte&0xFF);

    sh->length[0]+=8;

    if (sh->length[0]==0L) { sh->length[1]++; sh->length[0]=0L; }

    if ((sh->length[0]%512)==0) shs_transform(sh);

}

void shs256_hash(sha256 *sh,char hash[32])

{ /* pad message and finish - supply digest */

    int i;

    mr_unsign32 len0,len1;

    len0=sh->length[0];

    len1=sh->length[1];

    shs256_process(sh,PAD);

    while ((sh->length[0]%512)!=448) shs256_process(sh,ZERO);

    sh->w[14]=len1;

    sh->w[15]=len0;

    shs_transform(sh);

    for (i=0;i<32;i++)

    { /* convert to bytes */

        hash[i]=((sh->h[i/4]>>(8*(3-i%4))) & 0xffL);

    }

    shs256_init(sh);

}

/* test program: should produce digest

248d6a61 d20638b8 e5c02693 0c3e6039 a33ce459 64ff2167 f6ecedd4 19db06c1

#include <stdio.h>

#include "miracl.h"

char test[]="abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq";

int main()

{

    char hash[32];

    int i;

    sha256 sh;

    shs256_init(&sh);

    for (i=0;test[i]!=0;i++) shs256_process(&sh,test[i]);

    shs256_hash(&sh,hash);

    for (i=0;i<32;i++) printf("%02x",(unsigned char)hash[i]);

    printf("\n");

    return 0;

}

*/