Patent Document ID: 9992013
Application ID: 15078869
Patent Flag: 1

Claim One:
1. A method for protecting a cryptography device against side-channel attack while performing decryption according to a specified encryption scheme thereby rendering the cryptography device less vulnerable to attacks designed to cause the cryptography device to reveal information an attacker may use to discern cryptographic material stored on the cryptography device, the method comprising: receiving by the processor a code c, wherein c is a function of a key pair (having a public key and a secret key) and an error e; decrypting by the processor the code c by deriving the error e by: computing a polynomial syndrome S(z) which is a univariate polynomial deduced from c, but depending only on e, using a modified Extended Euclidean Algorithm having inputs a(z), b(z), and d, where a(z) and b(z) are polynomials and d is a public parameter of the encryption scheme to compute an error locator polynomial σ(z), by: iteratively performing a computation L a number of times defined by the parameter d, the computation L performing a fixed number of arithmetic operations regardless of Hamming weight of inputs a(z) and b(z), the arithmetic operations performing polynomial subtraction operations resulting in a result related to the result of a standard Extended Euclidean Algorithm, finding by the processor roots of σ(z); and inferring by the processor the error e from the roots of σ(z).