Patent ID: 8306220

Claim:
A computer-based method to generate an i-th private key in a public key encryption scheme with traceable private keys formed by a public component γ (i) and a secret component θ i , according to a maximal coalition factor k, with all arithmetic operations performed within a multiplicative group Z/qZ where q is a prime number, said method comprising: generating on a computer said public component according to: γ (i) =(1, i mod q,i 2 mod q, . . . ,i 2k-1 mod q ) and generating on a computer said secret component being defined as: θ i = ∑ r j ⁢ α j ∑ r j ⁢ γ j ( i ) ⁢ mod ⁢ ⁢ q where r j and α j are random values in the group Z/qZ.