commands → logmod

logmod(A,B,P)

The logmod command solves A = B^X mod P for non-negative integers, that is, it computes the logarithm of A to the base B modulo P. If the logarithm does not exist then null is returned.

Examples 

# solve 5 = 4^X mod 11
logmod(5,4,11);
	2

(4^2) % 11;
	5

Algorithm

The Pohlig-Hellman algorithm and Pollard's rho algorithm are used to compute discrete logarithms.

References

Link to Handbook of Applied Cryptography
Cohen, Henri. A Course in Computational Algebraic Number Theory. Springer, 1993.
Koblitz, Neal. A Course in Number Theory and Cryptography. Springer, 1998.