TweetNaclSharp

Port of TweetNaCl / NaCl to C#. Public domain.

Documentation

• Overview
• Installation
• Examples
• Usage
  • Public-key authenticated encryption (box)
  • Secret-key authenticated encryption (secretbox)
  • Scalar multiplication
  • Signatures
  • Hashing
  • Random bytes generation
  • Constant-time comparison
• System requirements
• Development and testing
• Contributors

Overview

The primary goal of this project is to produce a translation of TweetNaCl to C# which is as close as possible to the original C implementation, plus a thin layer of idiomatic high-level API on top of it.

There are two versions, you can use either of them:

• TweetNaclSharp.Nacl is the port of TweetNaCl with minimum differences from the original + high-level API.

• TweetNaclSharp.NaclFast is like TweetNaclSharp.Nacl, but with some functions replaced with faster versions.

Installation

You can install TweetNaclSharp via NuGet:

package manager:

$ PM> Install-Package TweetNaclSharp

NET CLI:

$ dotnet add package TweetNaclSharp

or download source code.

Examples

You can find usage examples in our wiki.

Usage

All API functions accept and return bytes as byte[]s. If you need to encode or decode strings, use functions from TweetNaclSharp.NaclUtil or one of the more robust codec packages.

Public-key authenticated encryption (box)

Implements x25519-xsalsa20-poly1305.

TweetNaclSharp.Nacl.BoxKeyPair()

Generates a new random key pair for box and returns it as an object with PublicKey and SecretKey members:

{
   PublicKey: ...,  // byte[] with 32-byte public key
   SecretKey: ...   // byte[] with 32-byte secret key
}

TweetNaclSharp.Nacl.BoxKeyPairFromSecretKey(secretKey)

Returns a key pair for box with public key corresponding to the given secret key.

TweetNaclSharp.Nacl.Box(message, nonce, theirPublicKey, mySecretKey)

Encrypts and authenticates message using peer's public key, our secret key, and the given nonce, which must be unique for each distinct message for a key pair.

Returns an encrypted and authenticated message, which is TweetNaclSharp.Nacl.BoxOverheadLength longer than the original message.

TweetNaclSharp.Nacl.BoxOpen(box, nonce, theirPublicKey, mySecretKey)

Authenticates and decrypts the given box with peer's public key, our secret key, and the given nonce.

Returns the original message, or null if authentication fails.

TweetNaclSharp.Nacl.BoxBefore(theirPublicKey, mySecretKey)

Returns a precomputed shared key which can be used in TweetNaclSharp.Nacl.BoxAfter and TweetNaclSharp.Nacl.BoxOpenAfter.

TweetNaclSharp.Nacl.BoxAfter(message, nonce, sharedKey)

Same as TweetNaclSharp.Nacl.Box, but uses a shared key precomputed with TweetNaclSharp.Nacl.BoxBefore.

TweetNaclSharp.Nacl.BoxOpenAfter(box, nonce, sharedKey)

Same as TweetNaclSharp.Nacl.BoxOpen, but uses a shared key precomputed with TweetNaclSharp.Nacl.BoxBefore.

Constants

TweetNaclSharp.Nacl.BoxPublicKeyLength = 32

Length of public key in bytes.

TweetNaclSharp.Nacl.BoxSecretKeyLength = 32

Length of secret key in bytes.

TweetNaclSharp.Nacl.BoxSharedKeyLength = 32

Length of precomputed shared key in bytes.

TweetNaclSharp.Nacl.BoxNonceLength = 24

Length of nonce in bytes.

TweetNaclSharp.Nacl.BoxOverheadLength = 16

Length of overhead added to box compared to original message.

Secret-key authenticated encryption (secretbox)

Implements xsalsa20-poly1305.

TweetNaclSharp.Nacl.Secretbox(message, nonce, key)

Encrypts and authenticates message using the key and the nonce. The nonce must be unique for each distinct message for this key.

Returns an encrypted and authenticated message, which is TweetNaclSharp.Nacl.SecretboxOverheadLength longer than the original message.

TweetNaclSharp.Nacl.SecretboxOpen(box, nonce, key)

Authenticates and decrypts the given secret box using the key and the nonce.

Returns the original message, or null if authentication fails.

Constants

TweetNaclSharp.Nacl.SecretboxKeyLength = 32

Length of key in bytes.

TweetNaclSharp.Nacl.SecretboxNonceLength = 24

Length of nonce in bytes.

TweetNaclSharp.Nacl.SecretboxOverheadLength = 16

Length of overhead added to secret box compared to original message.

Scalar multiplication

Implements x25519.

TweetNaclSharp.Nacl.ScalarMult(n, p)

Multiplies an integer n by a group element p and returns the resulting group element.

TweetNaclSharp.Nacl.ScalarMultBase(n)

Multiplies an integer n by a standard group element and returns the resulting group element.

Constants

TweetNaclSharp.Nacl.ScalarMultScalarLength = 32

Length of scalar in bytes.

TweetNaclSharp.Nacl.ScalarMultGroupElementLength = 32

Length of group element in bytes.

Signatures

Implements ed25519.

TweetNaclSharp.Nacl.SignKeyPair()

Generates new random key pair for signing and returns it as an object with PublicKey and SecretKey members:

{
   PublicKey: ...,  // byte[] with 32-byte public key
   SecretKey: ...   // byte[] with 64-byte secret key
}

TweetNaclSharp.Nacl.SignKeyPairFromSecretKey(secretKey)

Returns a signing key pair with public key corresponding to the given 64-byte secret key. The secret key must have been generated by TweetNaclSharp.Nacl.SignKeyPair or TweetNaclSharp.Nacl.SignKeyPairFromSeed.

TweetNaclSharp.Nacl.SignKeyPairFromSeed(seed)

Returns a new signing key pair generated deterministically from a 32-byte seed. The seed must contain enough entropy to be secure. This method is not recommended for general use: instead, use TweetNaclSharp.Nacl.SignKeyPair to generate a new key pair from a random seed.

TweetNaclSharp.Nacl.Sign(message, secretKey)

Signs the message using the secret key and returns a signed message.

TweetNaclSharp.Nacl.SignOpen(signedMessage, publicKey)

Verifies the signed message and returns the message without signature.

Returns null if verification failed.

TweetNaclSharp.Nacl.SignDetached(message, secretKey)

Signs the message using the secret key and returns a signature.

TweetNaclSharp.Nacl.SignDetachedVerify(message, signature, publicKey)

Verifies the signature for the message and returns true if verification succeeded or false if it failed.

Constants

TweetNaclSharp.Nacl.SignPublicKeyLength = 32

Length of signing public key in bytes.

TweetNaclSharp.Nacl.SignSecretKeyLength = 64

Length of signing secret key in bytes.

TweetNaclSharp.Nacl.SignSeedLength = 32

Length of seed for TweetNaclSharp.Nacl.SignKeyPairFromSeed in bytes.

TweetNaclSharp.Nacl.SignSignatureLength = 64

Length of signature in bytes.

Hashing

Implements SHA-512.

TweetNaclSharp.Nacl.Hash(message)

Returns SHA-512 hash of the message.

Constants

TweetNaclSharp.Nacl.HashHashLength = 64

Length of hash in bytes.

Random bytes generation

TweetNaclSharp.Nacl.RandomBytes(length)

Returns a byte[] of the given length containing random bytes of cryptographic quality.

Implementation note

TweetNaclSharp uses the following methods to generate random bytes, it runs on:

• System.Security.Cryptography.RandomNumberGenerator (standard)

If you somehow have a cryptographically-strong source of entropy (not Random!), and you know what you are doing, you can plug it into TweetNaclSharp like this:

TweetNaclSharp.Nacl.SetPRNG((byte[] x, int n) => {
  // ... copy n random bytes into x ...
});

Note that TweetNaclSharp.Nacl.SetPRNG completely replaces internal random byte generator with the one provided.

Constant-time comparison

TweetNaclSharp.Nacl.Verify(x, y)

Compares x and y in constant time and returns true if their lengths are non-zero and equal, and their contents are equal.

Returns false if either of the arguments has zero length, or arguments have different lengths, or their contents differ.

System requirements

TweetNaclSharp supports:

• Net 6

Development and testing

Make sure to rebuild projects every time you change code for testing.

Testing

To run tests:

$ dotnet test

Contributors

XeroXP.