JavaDataStructures/ECC/ECC.java at master · benaich/JavaDataStructures · GitHub

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package ECC;

import java.math.BigInteger;

import java.util.HashMap;

import java.util.Random;

public class ECC {

public static int PAD = 5;

public static final Random r = new Random();

private HashMap<Point, Integer> pointTable;

private HashMap<Integer, Point> charTable;

private Encoder mEncoder;

private Decoder mDecoder;

public ECC(EllipticCurve c) {

initCodeTable(c);

this.mEncoder = new Encoder(charTable);

this.mDecoder = new Decoder(pointTable);

}

public static Random getRandom() {

return r;

}

private int[] encrypt(String msg, PublicKey key) {

EllipticCurve c = key.getCurve();

Point g = c.getBasePoint();

Point publicKey = key.getKey();

BigInteger p = c.getP();

int numBits = p.bitLength();

BigInteger k;

do {

k = new BigInteger(numBits, getRandom());

} while (k.mod(p).compareTo(BigInteger.ZERO) == 0);

Point sharedSecret = c.multiply(publicKey, k);

Point keyHint = c.multiply(g, k); // key to send

System.out.println("----------------- Encryption process -----------------");

System.out.println(c);

System.out.println("Mesage to encrypt, m = " + msg);

System.out.println("Bob's public key, Pb = " + publicKey);

System.out.println("Alice's private key, k = " + k);

System.out.println("The ecryption key, sharedSecret = k * Pb = " + sharedSecret);

System.out.println("The hint to compute sharedSecret for bob, keyHint = " + keyHint);

Matrix mMatrix = mEncoder.encode(msg);

mMatrix.performAddition(Helpers.toBinary(sharedSecret));

System.out.println("sharedSecret binary format :");

Helpers.print(Helpers.toBinary(sharedSecret));

System.out.println("4) encrypt the matrix with sharedSecret (code addition)");

System.out.println(mMatrix);

return mMatrix.toArray(Helpers.toBinary(keyHint));

}

private String decrypt(int[] cipherText, PrivateKey key) {

EllipticCurve c = key.getCurve();

Point g = c.getBasePoint();

BigInteger privateKey = key.getKey();

BigInteger p = c.getP();

Point keyHint = Point.make(cipherText);

Point sharedSecret = c.multiply(keyHint, privateKey);

System.out.println("\n----------------- Decryption process -----------------");

System.out.println("1) Bob receive this :");

Helpers.print(cipherText);

System.out.println("");

System.out.println("2) Extract keyhint and the matrix C");

System.out.println("KeyHint = "+keyHint);

//get the decypted matrix

Matrix mMatrix = Matrix.make(cipherText);

System.out.println("C = ");

System.out.println(mMatrix);

//substract the key form the matrix

mMatrix.performSubstraction(Helpers.toBinary(sharedSecret));

System.out.println("Matrix after substraction");

System.out.println(mMatrix);

//decode the matrix

System.out.println("3) Reverse Matrix Scrambling");

return mDecoder.decode(mMatrix);

}

/**

* Generate a random key-pair, given the elliptic curve being used.

public static KeyPair generateKeyPair(EllipticCurve c) {

// Randomly select the private key, such that it is relatively prime to p

BigInteger p = c.getP();

BigInteger privateKey;

do {

privateKey = new BigInteger(p.bitLength(), getRandom());

} while (privateKey.mod(p).compareTo(BigInteger.ZERO) == 0);

// Calculate the public key, k * g.

Point g = c.getBasePoint();

Point publicKey = c.multiply(g, privateKey);

return new KeyPair(

new PublicKey(c, publicKey),

new PrivateKey(c, privateKey)

);

}

public final void initCodeTable(EllipticCurve curve) {

charTable = new HashMap<>();

pointTable = new HashMap<>();

Point p = curve.getBasePoint();

for (int i = 1; i < 27; i++) {

do {

p = curve.multiply(curve.getBasePoint(), i);

} while (p.isInfinity());

charTable.put(i + 96, p); // 0 here refers to char 97 witch is a

}

//special characters

charTable.put(32, Point.getInfinity()); //space

int[] codeAscii = new int[]{10, 13, 39, 40, 41, 44, 46, 58, 59};

for (int i : codeAscii) {

p = curve.add(p, curve.getBasePoint());

charTable.put(i, p);

}

//populate the points symbol table

for (Integer key : charTable.keySet()) {

pointTable.put(charTable.get(key), key);

}

public void displayCodeTable() {

System.out.println("------ Code Table -------");

charTable.forEach((cle, val) -> {

System.out.println((char) cle.intValue() + " -> " + val);

});

}

public static void main(String[] args) {

EllipticCurve c = new EllipticCurve(4, 20, 29, new Point(1, 5));

ECC ecc = new ECC(c);

ecc.displayCodeTable();

String msg = "i understood the importance in principle of public key cryptography, but it is all moved much faster than i expected i did not expect it to be a mainstay of advanced communications technology";

msg = "hi there";

// generate pair of keys

KeyPair keys = generateKeyPair(c);

// encrypt the msg

int[] cipherText = ecc.encrypt(msg, keys.getPublicKey());

System.out.println("5) Alice send this to Bob:");

Helpers.print(cipherText);

// decrypt the result

String plainText = ecc.decrypt(cipherText, keys.getPrivateKey());

System.out.println("\n5) Translate each point to a carracter");

//System.out.println("Cipher : ");

//Helpers.print(cipherText);

System.out.println("Plain text : \n" + plainText);

}

JavaDataStructures/ECC/ECC.java at master · benaich/JavaDataStructures · GitHub

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