Scrypto

Scrypto is an open source cryptographic toolkit designed to make it easier and safer for developers to use cryptography in their applications.

It was extracted from Scorex, open-source modular blockchain & cryptocurrency framework.

Public Domain.

If you want to check benchmarks for authenticated AVL+ trees, please visit dedicated repository. Use the repository as code examples for the trees also, though one code example is provided in "Authenticated Data Structures" section below.

Get Scrypto

Scrypto is available on Sonatype for Scala 2.12!

resolvers += "Sonatype Releases" at "https://oss.sonatype.org/content/repositories/releases/"

You can use Scrypto in your sbt project by simply adding the following dependency to your build file:

// For Scala 2.12
libraryDependencies += "org.consensusresearch" %% "scrypto" % "1.2.0"
// For Scala 2.11
libraryDependencies += "org.consensusresearch" %% "scrypto" % "1.2.0-RC3"

Hash functions

Supported hash algorithms are:

• Blake
• Blake2b
• BMW
• CubeHash
• Echo
• Fugue
• Groestl
• Hamsi
• JH
• Keccak
• Luffa
• Sha
• SHAvite
• SIMD
• Skein
• Whirlpool

Take a look at CryptographicHash interface and use supported hash algorithms like

Keccak512("some string or bytes")

All provided hash functions are secure, and their implementations are thread safe.

Hash chain

It's possible to apply hash functions sequentially to create more secure hash function. The most well-known X11 hash chain is available from this library.

You can easily create your own hash chain function:

import scorex.crypto.applyHashes
object MyCustomHash extends CryptographicHash {
  override val DigestSize: Int = 64
  override def hash(input: Message): Digest = applyHashes(input, Blake512, Sha512, Groestl512, Skein512)
}

or just

val myHashChain = hashChain(Blake512, BMW512, Groestl512, Skein512, JH512, Keccak512, Luffa512, Wirlpool)

Note, that hash chain will be as good as the strongest of the algorithms included in the chain.

Commutative hash

You can create commutative hash from any hash function with CommutativeHash case class like CommutativeHash(Sha256). A hash function h is commutative if h(x,y)==h(y,x) , for all x and y.

Binary-to-text Encoding Schemes

Scrypto has implementations of few binary-to-text encoding schemes:

• Base16
• Base58
• Base64

Example:

  val encoded = Base64.encode(data)
  val restored = Base64.decode(encoded)
  restored shouldBe data

Signing functions

Scrypto supports following elliptic curves:

• Curve25519(& Ed25519)

Example:

  val curveImpl = new Curve25519
  val keyPair = curveImpl.createKeyPair()
  val sig = curveImpl.sign(keyPair._1, message)
  assert(curveImpl.verify(sig, message, keyPair._2))

Note on security: Scrypto provides Scala wrapper for Curve25519-Java by Whisper Systems, so has the same security properties. JDK's SecureRandom used to obtain seed bytes.

Authenticated data structures

Scrypto supports authenticated AVL+ trees with the batching compression support and guaranteed verifier efficiency, see http://eprint.iacr.org/2016/994 for details. The implementation can be found in the scorex.crypto.authds.avltree.batch package. Here are code snippets on how to generate proofs and check them. In this example we demonstrate two batches of two modifications per batch, starting with the empty tree: in the first batch, a prover inserts two values into the tree; in the second batch, the prover updates the first value and deletes the second one.

• First, we create a prover and get an initial root hash from it (in a real application, this value is a public constant because anyone, including verifiers, can compute it by using the same two lines of code)

  val prover = new BatchAVLProver(keyLength = 1, valueLength = 8)
  val initRoot = prover.rootHash

• Second, we create the first batch of tree modifications, inserting keys 1 and 2 with values 0 for each

  val m1 = Insert(Array(1:Byte), Array.fill(8)(0:Byte))
  val m2 = Insert(Array(2:Byte), Array.fill(8)(0:Byte))

• Prover applies the two modifications to an empty tree, obtains the first batch proof, and announces the next root hash root1

  prover.performOneModification(m1)
  prover.performOneModification(m2)
  val proof1 = prover.generateProof
  val root1 = prover.rootHash

• A proof is just an array of bytes, so you can immediately send it over a wire or save it to a disk. Next, the prover performs two more modifications, obtains a second proof, and announces the second root hash root2

   val m3 = Update(Array(1:Byte), Array.fill(8)(1:Byte))
   val m4 = Remove(Array(2:Byte))
   prover.performOneModification(m3)
   prover.performOneModification(m4)
   val proof2 = prover.generateProof
   val root2 = prover.rootHash

• We now verify the proofs. For each batch, we construct a verifier using the digest that preceded the batch and the proof of the batch, and apply modifications. If verification fails, the verifier digest will equal None. Else, the verifier's new digest is the correct one for the tree as modified by the verifier. Furthermore, if the verifier performed the same modifications as the prover, then the verifier and prover digests will match.

  val verifier1 = new BatchAVLVerifier(initRoot, proof1, keyLength = 1, valueLength = 8)
  verifier1.performOneModification(m1)           
  verifier1.performOneModification(m2)
  verifier1.digest match {
    case Some(rt1) if rt1.sameElements(root1) =>
      //If announced root1 is already trusted, then verification of the second batch can simply start here
      val verifier2 = new BatchAVLVerifier(rt1, proof2, keyLength = 1, valueLength = 8)
      verifier2.performOneModification(m3)
      verifier2.performOneModification(m4)
      verifier2.digest match {
        case Some(rt2) if rt2.sameElements(root2) => println("declared root2 value and proofs are valid")
        case _ => println("second proof or announced root value NOT valid")
      }
    case _ =>
      println("first proof or announced root1 NOT valid")
  }

Note that the verifier has additional optional parameters that can be used to limit its maximum running time, to prevent a malicious prover from forcing the verifier to waste cycles.

Tests

Run sbt test from a folder contains the framework to launch tests.

License

The code is under Public Domain CC0 license means you can do anything with it. Full license text is in COPYING file

Contributing

Your contributions are always welcome! Please submit a pull request or create an issue to add a new cryptographic primitives or better implementations.