Description
QUAD relies on the iteration of a randomly chosen multivariate quadratic system S=(Q1, ..., Qm) of m=kn equations in n unknowns over a finite field GF(q). The keystream generation process simply consists in iterating the three following steps in order to produce (k -1) n GF(q) keystream values at each iteration.
- Compute the kn-tuple of GF(q) values S(x) = (Q1(x),..., Qkn(x)) where x is the current value of the internal state;
- Output the sequence (Qn+1(x),..., Qkn(x)) of (k-1)n GF(q) keystream values
- Update the internal state x with the sequence of n GF(q) first generated values (Q1(x),..., Qn(x))
QUAD is a modern stream cipher, i.e. it uses a key and an initialisation value (IV) to produce a keystream sequence. A Key and IV setup is also defined which also rely on multivariate quadratic system.
Read more about this topic: QUAD (cipher)
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