Umbral-rs

umbral-rs is the implementation of the Umbral threshold proxy re-encryption scheme, built with Rust taking as reference the Python version createdby the Umbral authors.

Umbral consists of a Proxy Re-Encryption scheme, in which a data holder can delegate decryption rights to a data consumer for any encrypted text intended for him/her. It is carried out through a re-encryption process performed by a series of semi-trusted proxies. When a threshold of these proxies participates by performing the re-encryption and creating some shares, the consumer is able to combine these independent re-encryption shares and decrypt the original message using his private key.

Encrypt/Decrypt Example

use umbral_rs::pre::*;

let params = new_standard_params();
let alice = KeyPair::new(&params);
let signer = Signer::new(&params);
let bob = KeyPair::new(&params);

let plaintext = b"Hello, umbral!".to_vec();
let (ciphertext, mut capsule) = encrypt(&alice.public_key(), &plaintext).unwrap();

capsule.set_correctness_keys(&alice.public_key(), &bob.public_key(), &signer.public_key());

let threshold = 2;
let nodes_number = 5;

let kfrags = generate_kfrags(
  &alice,
  &bob.public_key(),
  threshold,
  nodes_number,
  &signer,
  KFragMode::DelegatingAndReceiving,
).unwrap();

for kfrag in kfrags {
  let cfrag = reencrypt(&kfrag, &capsule, true, None, true).unwrap();
  capsule.attach_cfrag(&cfrag).unwrap();
}

let plaintext_bob = decrypt(ciphertext, &capsule, &bob, true).unwrap();
assert_eq!(plaintext, plaintext_bob);
println!("{:?}", String::from_utf8(plaintext_bob.to_owned()).unwrap());

file documentation

the source code is in the src folder, the documentation is in the docs folder. Stated briefly, inside the src/internal folder there are the following files:

• keys.rs contains the KeyPair struct, which is used to generate the public and private keys.
• capsule.rs contains the Capsule struct, which is used to encapsulate the ciphertext.
• kfrag.rs contains the KFrag struct, which is used to delegate the re-encryption rights.
• curve.rs contains the Curve struct, which is used to generate the curve parameters.
• errors.rs contains the UmbralError enum, which is used to return the errors.
• scheme.rs contains the hashing functions used in the scheme.
• utils.rs contains tilities functions such as poly_eval used to evaluate a polynomial at a point.

In the src folder there are the following files:

• pre.rs contains the main functions to use the library, such as encrypt, decrypt, reencrypt, generate_kfrags, etc.
• lib.rs contains the prelude module, which is used to import the main functions of the library.
• main.rs contains the main function, which is used to run the tests.