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FULLY HOMOMORPHIC ENCRYPTION: CURRENT STATE OF THE ...

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“Polly Cracker”: An Early Attempt at SWHE<br />

[Fellows-Koblitz ‘93]<br />

Main Idea<br />

Encryptions of 0 evaluate to 0 at the secret key.<br />

�� KeyGen: Secret = some point s = (s (s1, 1, …,s …,sn) 2 Z n<br />

n) 2 Z n<br />

q .<br />

Public key: Polynomials {ai(x1,…,xn)} s.t. ai(s)=0 mod q.<br />

� Encrypt: From {ai}, generate a random polynomial b(x)<br />

such that b(s) = 0 mod q. For m in {0,1}, ciphertext is:<br />

c(x) = m + b(x) mod q.<br />

� Decrypt: Evaluate ciphertext at secret: c(s)=m mod q.<br />

� ADD and MULT: Output sum or product of ciphertexts.

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