Org.BouncyCastle.Math.BigInteger.Mod C# (CSharp) Method

		public BigInteger Mod(
			BigInteger m)
		{
			if (m.sign < 1)
				throw new ArithmeticException("Modulus must be positive");

			BigInteger biggie = Remainder(m);

			return (biggie.sign >= 0 ? biggie : biggie.Add(m));
		}

        /// <summary>
        /// Constructor which attempts to redeem a completed set of three codes, and calculate the private key.
        /// </summary>
        public EscrowCodeSet(string code1, string code2, string code3)
        {
            if (code1 == null || code2 == null || code3 == null || code1 == "" || code2 == "" || code3 == "") {
                throw new ArgumentException("Three codes are required to use this function.");
            }

            string codea = null, codeb=null, codep = null;

            if (code1.StartsWith("einva")) codea = code1;
            if (code2.StartsWith("einva")) codea = code2;
            if (code3.StartsWith("einva")) codea = code3;
            if (code1.StartsWith("einvb")) codeb = code1;
            if (code2.StartsWith("einvb")) codeb = code2;
            if (code3.StartsWith("einvb")) codeb = code3;
            if (code1.StartsWith("einvp")) codep = code1;
            if (code2.StartsWith("einvp")) codep = code2;
            if (code3.StartsWith("einvp")) codep = code3;

            if (codea==null || codeb == null || codep == null) {
                throw new ArgumentException("In order to use this function, one code MUST be an Escrow Invitation A (starting " +
                    "with \"einva\"), one must be an Escrow Invitation B (starting with \"einvb\") and the last " +
                    "code MUST be a Payment Invitation (starting with \"einvp\").");
            }

            byte[] pubparta, privparta;
            int identifier30a;
            string failreason = parseEscrowCode(codea, out pubparta, out privparta, out identifier30a);
            if (failreason != null) throw new ArgumentException("Escrow Invitation Code A: " + failreason);

            byte[] pubpartb, privpartb;
            int identifier30b;
            failreason = parseEscrowCode(codeb, out pubpartb, out privpartb, out identifier30b);
            if (failreason != null) throw new ArgumentException("Escrow Invitation Code B: " + failreason);

            if (identifier30a != identifier30b) {
                throw new ArgumentException("The two Escrow Invitations are not mates and cannot unlock the private key.");
            }

            string notvalid = "Not a valid Payment Invitation Code";
            string notvalid2 = "Code is not a valid Payment Invitation Code or may have a typo or other error.";
            string notvalid3 = "The Payment Invitation does not belong to the provided Escrow Invitation.";

            long headp;
            byte[] invbytesp;
            string failReason = parseEitherCode(codep, notvalid, notvalid2, out invbytesp, out headp);

            if (headp < headbaseP) throw new ArgumentException(notvalid);
            long identifier30L = headp - headbaseP;
            if (identifier30L < 0 || identifier30L > 0x3FFFFFFFL) throw new ArgumentException(notvalid);

            if (identifier30L != (long)identifier30a) {
                throw new ArgumentException("The Payment Invitation was not generated from either of the provided Escrow Invitation codes and cannot be unlocked by them.");
            }

            byte[] privpartz = new byte[32];
            Array.Copy(invbytesp, 8 + 1 + 1, privpartz, 0, 32);
            byte networkByte = invbytesp[8];
            bool compressedFlag = (invbytesp[8 + 1 + 1 + 32 + 20] & 0x1) == 1;

            // get private key
            BigInteger xyz = new BigInteger(1, privparta).Multiply(new BigInteger(1, privpartb)).Multiply(new BigInteger(1, privpartz));
            var ps = Org.BouncyCastle.Asn1.Sec.SecNamedCurves.GetByName("secp256k1");
            xyz = xyz.Mod(ps.N);

            KeyPair kp = new KeyPair(xyz, compressedFlag, networkByte);

            // provide everything
            this.EscrowInvitationCodeA = codea;
            this.EscrowInvitationCodeB = codeb;
            this.PaymentInvitationCode = codep;
            this.BitcoinAddress = kp.AddressBase58;
            this.PrivateKey = kp.PrivateKey;
        }