javallier

A Java library for Paillier partially homomorphic encryption based on python-paillier.

The homomorphic properties of the paillier cryptosystem are:

• Encrypted numbers can be multiplied by a non encrypted scalar.
• Encrypted numbers can be added together.
• Encrypted numbers can be added to non encrypted scalars.

To use the library add the following dependency to your SBT configuration:

libraryDependencies += "com.n1analytics" % "javallier_2.10" % "0.6.0"

Example usages are provided in the /examples source directory. A benchmarking script can be found in /benchmark.

Build

Compile the library:

$ sbt compile

Create a jar file:

$ sbt package

Run all tests with sbt:

$ sbt test

Or run just fast tests:

$ ./test-fast.sh

Command Line Tool

A small command line tool has been created to wrap the javallier library.

Use the javallier cli tool to:

• generate and serialize key pairs (of different key sizes)
• encrypt and serialize signed floating point numbers given a public key
• add two encrypted numbers together
• add an encrypted number to a plaintext number
• multiply an encrypted number by a plaintext number
• decrypt an encrypted number given the private key

Build the javallier CLI tool:

sbt assembly

This creates a javallier.jar jar file in:

./target/scala-2.10

To run it:

java -jar javallier.jar <COMMAND>  

Alternatively you can run directly with sbt:

sbt "runMain com.n1analytics.paillier.cli.Main"

Example CLI session

$ java -jar javallier.jar genpkey --keysize 256 -m "Example keypair" examplekey.priv
$ cat examplekey.priv | python -m json.tool
{
    "kty": "DAJ",
    "key_ops": [
        "decrypt"
    ],
    "pub": {
        "alg": "PAI-GN1",
        "kty": "DAJ",
        "kid": "Example keypair",
        "n": "AI9TjNmoL7p3j_D-RNK5AJQC1uDMtVvdy0MNi6ctj6Xn",
        "key_ops": [
            "encrypt"
        ]
    },
    "kid": "Example keypair",
    "lambda": "AI9TjNmoL7p3j_D-RNK5AJJ3odV_yUj39nLtFBMcrsoQ",
    "mu": "MDo136LqeN-R5W4kT2azGc6Y-cD77f6r_B6zncj48Eo"
}


$ java -jar javallier.jar extract examplekey.priv examplekey.pub
$ java -jar javallier.jar encrypt examplekey.pub "12" -o encA.json
$ java -jar javallier.jar encrypt examplekey.pub "8" -o encB.json
$ java -jar javallier.jar addenc examplekey.pub encA.json encB.json -o encC.json
$ java -jar javallier.jar decrypt examplekey.priv encC.json
20.0
$ java -jar javallier.jar add -o encD.json examplekey.pub encA.json 12
$ java -jar javallier.jar decrypt examplekey.priv encD.json
24.0

Releases

Releases will be signed by Brian Thorne with the PGP key 22AD F3BF C183 47DE

Creating a release

Update the version in build.sbt using semantic versioning. Update the CHANGELOG, git tag the new release.

Ensure you have sonatype credentials in ~/.sbt/0.13/sonatype.sbt, and install the pgp plugin (~/.sbt/0.13/plugins/pgp.sbt). Run sbt publishSigned, then visit the staging repositories of sonatype. Close the staging repository which will allow you to move to the release channel. Once you have successfully closed the staging repository, you can release it.

For more information:

• http://www.scala-sbt.org/release/docs/Using-Sonatype.html
• http://central.sonatype.org/pages/releasing-the-deployment.html

Limitation

Adding two encrypted numbers where the exponents differs wildly may result in overflow in the EncryptedNumber domain. The addition result can be successfully decrypted and decoded but the computation result is incorrect. Current implementation does not detect such overflow.