tweetnacl-js | Port of TweetNaCl cryptographic library to JavaScript | Cryptography library

TweetNaCl.js is a port to JavaScript of TweetNaCl. TweetNacl in turn is a compact implementation of NaCl, which provides various encryption and signature algorithms essentially based on Curve25519. There are NaCl-compatible implementations or wrappers for many platforms, so that any of these documentations can be used for an introduction, e.g. the clear documentation of the Libsodium fork.

The documentation of TweetNaCl.js also gives a short overview of the functionality: nacl.sign(message, secretKey) creates a signed message consisting of the 64 bytes signature with attached message. nacl.sign.open(signedMessage, publicKey) verifies the message using the signature and returns the message if verification is successful. The algorithm used for signing is Ed25519.

As already noted in the comments, you do not distinguish clearly between encryption (purpose: secrecy) and signing (purpose: authentication / integrity). In particular, secrecy of the message is not the purpose of signing. This becomes apparent e.g. when the return of nacl.sign() contains the unencrypted message (see code snippet below). However, it is true that encryption with the private key is performed during signing (but not for the purpose of keeping it secret).

The following implementation is a pure JavaScript implementation: