What is Branca?
Branca is a secure easy to use token format which makes it hard to shoot yourself in the foot. It uses IETF XChaCha20-Poly1305 AEAD symmetric encryption to create encrypted and tamperproof tokens. The enrypted token is base62 encoded which makes it URL safe. Payload itself is an arbitrary sequence of bytes. You could use a JSON object, plain text string or even binary data serialized by MessagePack or Protocol Buffers.
Secure by design
There is no algorithm agility. The only supported cipher suite is IETF XChaCha20-Poly1305 AEAD. By removing the choice it is hard to shoot yourself in the foot.
Easy to implement
For developers a fast implementation of the chosen cipher suite is offered by the Sodium crypto library. Sodium is a modern, easy-to-use software crypto library.
By using authenticated encryption integrity of the token can be guaranteed. This means a possible attacker cannot alter the contents of a token.