OAEP_ENCODE: function()

in src/rsa.js [338:398]
49 lines of code
11 McCabe index (conditional complexity)

        OAEP_ENCODE: function(sha, m, rng, p) {
            var olen = RSA.RFS - 1,
                mlen = m.length,
                SEED = [],
                DBMASK = [],
                f = [],
                hlen,
                seedlen,
                slen,
                i, d, h;

            seedlen = hlen = sha;

            if (mlen > olen - hlen - seedlen - 1) {
                return null;
            }

            h = this.hashit(sha, p, -1);
            for (i = 0; i < hlen; i++) {
                f[i] = h[i];
            }

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

            for (i = 0; i < slen; i++) {
                f[hlen + i] = 0;
            }
            f[hlen + slen] = 1;
            for (i = 0; i < mlen; i++) {
                f[hlen + slen + 1 + i] = m[i];
            }

            for (i = 0; i < seedlen; i++) {
                SEED[i] = rng.getByte();
            }
            this.MGF1(sha, SEED, olen - seedlen, DBMASK);

            for (i = 0; i < olen - seedlen; i++) {
                DBMASK[i] ^= f[i];
            }
            this.MGF1(sha, DBMASK, seedlen, f);

            for (i = 0; i < seedlen; i++) {
                f[i] ^= SEED[i];
            }

            for (i = 0; i < olen - seedlen; i++) {
                f[i + seedlen] = DBMASK[i];
            }

            /* pad to length RFS */
            d = 1;
            for (i = RSA.RFS - 1; i >= d; i--) {
                f[i] = f[i - d];
            }
            for (i = d - 1; i >= 0; i--) {
                f[i] = 0;
            }

            return f;
        },