jpaillier's Introduction

jPaillier

A Java implementation of Paillier cryptosystem.

This library is developed as part of the research project CoPPDA (Corporate Privacy Preserving Data Analysis, http://www.enterprise-application-development.org/projects/coppda.html). There it is used for the implementation of different privacy preserving data minin methods.

WARNING: This library is developed for research, also it is in an early state and therefor NOT production ready.

Usage

create a key pair:

    KeyPairBuilder keygen = new KeyPairBuilder();
    keyPair = keygen.generateKeyPair();

encryption:

	PublicKey publicKey = keyPair.getPublicKey();
    BigInteger ciphertext = publicKey.encrypt(plainData);

decrypt a ciphertext:

    BigInteger decryptedData = keyPair.decrypt(ciphertext);

Homomorphic Addition

An interesting feature of the Paillier cryptosystem is its homomophic properties. The following example demonstrates how this library can be used to compute the homomorphic addition of two plaintext input values.

	BigInteger plainA = BigInteger.valueOf(102);
	BigInteger plainB = BigInteger.valueOf(203);

	BigInteger encryptedA = publicKey.encrypt(plainA);
	BigInteger encryptedB = publicKey.encrypt(plainB);
	
	BigInteger encryptedProduct = encryptedA.multiply(encryptedB).mod(publicKey.getnSquared());

	BigInteger additionResult = keypair.decrypt(encryptedProduct);
		
	// additionResult = 102 + 203 = 305

See the references for details. More examples can be found in the file: HomomorphicPropertiesTest.

##References

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