# Privacy

During the deployment of DREP Chain, it is inevitable that information to third parties might be disseminated due to data sharing via the internal Smart Pipeline. In order to eliminate such occurrences and to promote maximum user security and privacy, DREP Chain adopts the use of homomorphic encryption to safeguard users’ sensitive information.

DREP Chain’s homomorphic encryption utilizes the Paillier technique. It is computed based on the n-th residual classes of a quadratic integer group.

Where m stands for a message to be encrypted and m∈(0,n), then select random r∈(0,n) via generated key pairing: public key (n,g) and private key (λ,u), compute ciphertext C as C=gmrn modn2.

Ciphertext C is both a homomorphic and homomorphic mixed multiplication plaintext12, that is

• Homomorphic addition of plaintexts

D(E(m1,r1)E(m2,r2) mod n2)=m1+m2 mod n

D(E(m1,r1)gm2 mod n2)=m1+m2 mod n

• Homomorphic mixed multiplication of plaintexts

D(E(m1,r1)m2 mod n2)=m1m2 mod n

A variety of data processing can also be performed after encryption, with the results transmitted back to the users. With the use of private keys, users will be able to obtain the same set of results as with plain text processing, and yet minimizing the possibility of data leakage. In addition, homomorphic cryptographic signatures could be added to various contents, thereby enabling the possibility to verify misprocessing, spoofing and other forms of misconduct during data processing to ensure data accuracy.