How it works

Umbral is NuCypher's split-key threshold proxy re-encryption scheme. With Umbral, Alice (the data owner) can delegate decryption rights to Bob for any ciphertext encrypted for her, through a re-encryption process performed by a set of semi-trusted proxies. When a threshold number of these proxies participate by performing re-encryption, Bob is able to combine these independent re-encryptions and decrypt the original message using his private key.