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MCJL - Milagro Crypto Java Library
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/*
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
*/

/* Elliptic Curve API high-level functions  */

package org.apache.milagro.amcl.SECP256K1;

import org.apache.milagro.amcl.RAND;
import org.apache.milagro.amcl.HASH256;
import org.apache.milagro.amcl.HASH384;
import org.apache.milagro.amcl.HASH512;
import org.apache.milagro.amcl.AES;

public final class ECDH {
	public static final int INVALID_PUBLIC_KEY=-2;
	public static final int ERROR=-3;
	public static final int INVALID=-4;
	public static final int EFS=BIG.MODBYTES;
	public static final int EGS=BIG.MODBYTES;
//	public static final int EAS=16;
//	public static final int EBS=16;

//	public static final int SHA256=32;
//	public static final int SHA384=48;
//	public static final int SHA512=64;


//	public static final int HASH_TYPE=SHA512;


/* Convert Integer to n-byte array */
	public static byte[] inttoBytes(int n,int len)
	{
		int i;
		byte[] b=new byte[len];

		for (i=0;i0 && i>0)
		{
			i--;
			b[i]=(byte)(n&0xff);
			n/=256;
		}	
		return b;
	}

	public static byte[] hashit(int sha,byte[] A,int n,byte[] B,int pad)
	{
		byte[] R=null;

		if (sha==ECP.SHA256)
		{
			HASH256 H=new HASH256();
			H.process_array(A); if (n>0) H.process_num(n);
			if (B!=null) H.process_array(B);
			R=H.hash();
		}
		if (sha==ECP.SHA384)
		{
			HASH384 H=new HASH384();
			H.process_array(A); if (n>0) H.process_num(n);
			if (B!=null) H.process_array(B);
			R=H.hash();
		}
		if (sha==ECP.SHA512)
		{
			HASH512 H=new HASH512();
			H.process_array(A); if (n>0) H.process_num(n);
			if (B!=null) H.process_array(B);
			R=H.hash();
		}
		if (R==null) return null;

		if (pad==0) return R;
/* If pad>0 output is truncated or padded to pad bytes */
		byte[] W=new byte[pad];
		if (pad<=sha) 
		{
			for (int i=0;iolen) for (int i=0;iolen) for (int i=0;i32) b=128;
		byte[] B;
		byte[] K0=new byte[b];
		int olen=tag.length;

		//b=K0.length;
		if (olen<4 /*|| olen>sha*/) return 0;

		for (int i=0;i b) 
		{
			B=hashit(sha,K,0,null,0);
			for (int i=0;i=C.length) {fin=true; break;}  
				else ch=C[ipt++];  
			}
			a.decrypt(buff);
			if (fin) break;
			for (i=0;i<16;i++)
				MM[opt++]=buff[i];
		}    

		a.end();
		bad=false;
		padlen=buff[15];
		if (i!=15 || padlen<1 || padlen>16) bad=true;
		if (padlen>=2 && padlen<=16)
			for (i=16-padlen;i<16;i++) if (buff[i]!=padlen) bad=true;
    
		if (!bad) for (i=0;i<16-padlen;i++)
					MM[opt++]=buff[i];

		if (bad) return new byte[0];

		byte[] M=new byte[opt];
		for (i=0;i0)
		//{
		//	s.mod2m(2*ROM.AES_S);
		//}
		s.toBytes(S);

		WP=G.mul(s);
		WP.toBytes(W,false);  // To use point compression on public keys, change to true 

		return res;
	}

/* validate public key. */
	public static int PUBLIC_KEY_VALIDATE(byte[] W)
	{
		BIG r,q,k;
		ECP WP=ECP.fromBytes(W);
		int nb,res=0;

		r=new BIG(ROM.CURVE_Order);

		if (WP.is_infinity()) res=INVALID_PUBLIC_KEY;

		if (res==0)
		{

			q=new BIG(ROM.Modulus);
			nb=q.nbits();
			k=new BIG(1); k.shl((nb+4)/2);
			k.add(q);
			k.div(r);

			while (k.parity()==0)
			{
				k.shr(1);
				WP.dbl();
			}

			if (!k.isunity()) WP=WP.mul(k);
			if (WP.is_infinity()) res=INVALID_PUBLIC_KEY; 
		}
		return res;
	}

/* IEEE-1363 Diffie-Hellman online calculation Z=S.WD */
	public static int SVDP_DH(byte[] S,byte[] WD,byte[] Z)    
	{
		BIG r,s,wx,wy,z;
		int valid;
		ECP W;
		int res=0;
		byte[] T=new byte[EFS];

		s=BIG.fromBytes(S);

		W=ECP.fromBytes(WD);
		if (W.is_infinity()) res=ERROR;

		if (res==0)
		{
			r=new BIG(ROM.CURVE_Order);
			s.mod(r);

			W=W.mul(s);
			if (W.is_infinity()) res=ERROR; 
			else 
			{
				W.getX().toBytes(T);
				for (int i=0;i0)
			//{
			//	u.mod2m(2*ROM.AES_S);
			//}			
			V.copy(G);
			V=V.mul(u);   		
			vx=V.getX();
			c.copy(vx);
			c.mod(r);
			if (c.iszilch()) continue;

			u.copy(BIG.modmul(u,w,r));

			u.invmodp(r);
			d.copy(BIG.modmul(s,c,r));
			d.add(f);

			d.copy(BIG.modmul(d,w,r));

			d.copy(BIG.modmul(u,d,r));
		} while (d.iszilch());
       
		c.toBytes(T);
		for (int i=0;i=0 || d.iszilch() || BIG.comp(d,r)>=0) 
            res=INVALID;

		if (res==0)
		{
			d.invmodp(r);
			f.copy(BIG.modmul(f,d,r));
			h2=BIG.modmul(c,d,r);

			WP=ECP.fromBytes(W);
			if (WP.is_infinity()) res=ERROR;
			else
			{
				P=new ECP();
				P.copy(WP);
				P=P.mul2(h2,G,f);
				if (P.is_infinity()) res=INVALID;
				else
				{
					d=P.getX();
					d.mod(r);
					if (BIG.comp(d,c)!=0) res=INVALID;
				}
			}
		}

		return res;
	}

/* IEEE1363 ECIES encryption. Encryption of plaintext M uses public key W and produces ciphertext V,C,T */
	public static byte[] ECIES_ENCRYPT(int sha,byte[] P1,byte[] P2,RAND RNG,byte[] W,byte[] M,byte[] V,byte[] T)
	{ 
		int i,len;

		byte[] Z=new byte[EFS];
		byte[] VZ=new byte[3*EFS+1];
		byte[] K1=new byte[ECP.AESKEY];
		byte[] K2=new byte[ECP.AESKEY];
		byte[] U=new byte[EGS];

		if (KEY_PAIR_GENERATE(RNG,U,V)!=0) return new byte[0];  
		if (SVDP_DH(U,W,Z)!=0) return new byte[0];     

		for (i=0;i<2*EFS+1;i++) VZ[i]=V[i];
		for (i=0;i