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A Java API to TweetNaCl implementations. The following subset of the 25 functions in [TWEET-1] are supported:

  • crypto_sign_keypair.
  • crypto_sign.
  • crypto_sign_open.
  • crypto_box_keypair.
  • crypto_box_beforenm.
  • crypto_box_afternm.
  • crypto_box_open_afternm.
  • crypto_hash.

crypto_sign_x functions implement the ed25519 signature scheme. crypto_box_x functions implement public key authenticated encryption using x25519+xsalsa20+poly1305.

Our approach is to follow the original TweetNaCl/NaCl C API closely as documented at [NACL] and implemented in the TweetNaCl source code available at [TWEET-2].

Two implementations are supported

  1. The pure Java implementation from

  2. The native Libsodium implementation that is typically much faster than the Java version. See:

Comments, implementation approach, etc:

  • Unlike the TweetNaCl original, this library does not depend on random data. All functions are pure functions; they are deterministic.

  • C functions that always return 0 are implemented in Java using Java methods with the "void" return type.

  • Exceptions are sometimes used instead of returning an error code.

  • Byte arrays are used with their lengths. That is, we do not pass in offsets and size to allow for C-like array operations.

  • Memory allocation is normally done by the caller.

  • Input arguments are not normally checked. For example, a NullPointerException may be thrown when an argument is null the first time the argument is used.

salt-aa is "Powered by Curve25519".


To use the lib:

  1. Create a SaltLib instance with:

    SaltLib lib = SaltLibFactory.getLib()

  2. Then use the lib instance.

If you want to choose implementation specifically, call SaltLibFactory.getLib(LibType.JAVA) or SaltLib.getLib(LibType.NATIVE).

The build the lib, use ANT and build.xml.


To create a Java Eclipse project:

  • Add src/ and src-test/ to source path.
  • Add native libs according to lib-native/
  • Set out/classes as output for compiled Java classes.

Performance testing

See package saltaa.nperf for performance testing. Run class nperf.NTestRunner or EncryptPerformance.


  • TWEET-1. Daniel J. Bernstein, Bernard van Gastel, Wesley Janssen, Tanja Lange, Peter Schwabe, Sjaak Smetsers. TweetNaCl: a crypto library in 100 tweets. LatinCrypt 2014, to appear.

  • TWEET-2. Website:

  • NACL. Website: