Patent ID: 8774408

Claim:
A method, carried out on a computerized platform, for decryption, the method comprising: receiving a cryptogram C r (M), where M is a plaintext content and C r is a predetermined encryption algorithm; receiving an input parameter comprising a word r of n bits related to C r (M); given two pseudo-random functions g 0 and g 1 from m bits to m bits obtaining, on the basis of r, a derived value K r of m bits, wherein K r =g r n ∘ . . . g r 2 ∘g r 1 ( S ), where, for i=1, . . . , n, g r i =g 0 if r i =0, and g r i =g 1 if r i =1, and where S is a master value of m bits, wherein S is not disclosed to said user; conducting a search from among a set of words of m bits U j , where j=1, . . . , p recorded in a table T U and equal to U j =g v l(j) (j) ∘ . . . g v 2 (j) ∘g v 1 (j) ( S ), where, for i=1, . . . , l(j), the indices v i (j) are predetermined bits, for a word U σ equal to U σ =g r l(σ) ∘ . . . g r 2 ∘g r 1 ( S ), obtaining K r by calculating K r =g r n ∘ . . . g r l(σ)+1 ( U σ ); and decrypting C r (M) using, as a decryption key, a value obtained on the basis of at least one derived value K r , so as to obtain M.