Abstract:
A polynomial representation (bi(x)) in an AES finite field ( Z 2 [ x ] ( r ( x ) ) ) of input bytes (bi) of a state matrix (B) is obtained. A plurality (1) of irreducible polynomials (fi(y)) and a moving map (ψi) are used to map each polynomial (bi(x)) of the polynomial representation into a respective field of polynomials ( Z 2 [ y ] ( f i ( y ) ) ) computed with respect to one of the irreducible polynomials (fi(y)), to obtain respective moved polynomials (αi(y)). The moved polynomials (αi(y)) are mapped into a polynomial (a(z)) of a polynomial ring ( Z 2 [ z ] ( p ( z ) ) ) , obtained by applying an isomorphism (ω) between the fields of polynomials ( Z 2 [ y ] ( f i ( y ) ) ) and the polynomial ring ( Z 2 [ z ] ( p ( z ) ) ) based upon the Chinese remainder theorem (CRT). AES encryption is applied to the polynomial (a(z)). The polynomial (a(z)) is reconverted into the AES finite field ( Z 2 [ x ] ( r ( x ) ) ) to obtain an encrypted state matrix (CB).
Abstract:
A polynomial representation (bi(x)) in an AES finite field ( Z 2 [ x ] ( r ( x ) ) ) of input bytes (bi) of a state matrix (B) is obtained. A plurality (1) of irreducible polynomials (fi(y)) and a moving map (ψi) are used to map each polynomial (bi(x)) of the polynomial representation into a respective field of polynomials ( Z 2 [ y ] ( f i ( y ) ) ) computed with respect to one of the irreducible polynomials (fi(y)), to obtain respective moved polynomials (αi(y)). The moved polynomials (αi(y)) are mapped into a polynomial (a(z)) of a polynomial ring ( Z 2 [ z ] ( p ( z ) ) ) , obtained by applying an isomorphism (ω) between the fields of polynomials ( Z 2 [ y ] ( f i ( y ) ) ) and the polynomial ring ( Z 2 [ z ] ( p ( z ) ) ) based upon the Chinese remainder theorem (CRT). AES encryption is applied to the polynomial (a(z)). The polynomial (a(z)) is reconverted into the AES finite field ( Z 2 [ x ] ( r ( x ) ) ) to obtain an encrypted state matrix (CB).