int OAEP_ENCODE()

in src/rsa_support.c [171:211]

• 30 lines of code
• 3 McCabe index (conditional complexity)

int OAEP_ENCODE(int sha,const octet *m,csprng *RNG,const octet *p,octet *f)
{
    int slen;
    int olen=f->max-1;
    int mlen=m->len;
    int hlen;
    int seedlen;
    char dbmask[MAX_RSA_BYTES];
    char seed[64];
    octet DBMASK= {0,sizeof(dbmask),dbmask};
    octet SEED= {0,sizeof(seed),seed};

    hlen=seedlen=sha;
    if (mlen>olen-hlen-seedlen-1) return 1;
    if (m==f) return 1;  /* must be distinct octets */

    hashit(sha,p,-1,f);

    slen=olen-mlen-hlen-seedlen-1;

    OCT_jbyte(f,0,slen);
    OCT_jbyte(f,0x1,1);
    OCT_joctet(f,m);

    OCT_rand(&SEED,RNG,seedlen);

    MGF1(sha,&SEED,olen-seedlen,&DBMASK);

    OCT_xor(&DBMASK,f);
    MGF1(sha,&DBMASK,seedlen,f);

    OCT_xor(f,&SEED);

    OCT_joctet(f,&DBMASK);

    OCT_pad(f,f->max);
    OCT_clear(&SEED);
    OCT_clear(&DBMASK);

    return 0;
}