Homomorphic encryption explained: PHE vs FHE and blockchain uses
Thread298 words
Introduces homomorphic encryption as computing directly on ciphertext, distinguishing partially from fully homomorphic schemes and noting limits: efficiency, large ciphertexts and trusted setup needs.
Key claims
FHE allows arbitrary computation on ciphertext while PHE supports limited operations
0/ What is Homomorphic Encryption (HE)? 馃鈥嶁檪锔忊湪
(0/10) 馃У馃憞
1/ HE is a cryptographic tool that allows you to perform certain types of computations directly on the homomorphically encrypted ciphertext, generating the same results as if you performed the operations on the plaintext.
2/ There are two types of HE: partially homomorphic encryption (PHE) & fully homomorphic encryption (FHE). PHE allows for a limited number of operations on the ciphertext (e.g. addition or multiplication), while FHE allows for any computation to be performed on the ciphertext.
3/ HE can significantly improve transaction confidentiality and user anonymity in public blockchain networks by allowing data to be encrypted and remain so even during computational processes.
4/ To illustrate how FHE works, let's look at an example. Suppose Alice wants to send Bob a message containing the result of a complex computation, but wants to keep the message private from any observers.
5/ Alice and Bob agree on a set of parameters and an encryption scheme that allows for any computation to be performed on the ciphertext. Alice generates a public key and private key, and sends the public key to Bob.
6/ Alice encrypts the message (result of complex computation) using her private key and the agreed-upon encryption scheme, resulting in the ciphertext c. Alice sends c to Bob.
7/ Bob uses the public key to decrypt the ciphertext c and obtains the original message (result of complex computation). He can verify the message is correct by performing the same computation and checking the result.
8/ While FHE has limitations (e.g. limited efficiency, large ciphertext size, need for a trusted setup), it is expected to play an increasingly important role in the blockchain ecosystem in the coming years.
10/ Stay tuned for follow-up threads covering other upcoming privacy technologies! 馃鈥嶁檪锔忊湪