The original Pretty Good Privacy (PGP) by Philip Zimmermann in 1994 used only a sieve that divided by all known 16-bit primes (this table was produced using the

The original Pretty Good Privacy (PGP) by Philip Zimmermann in 1994 used only a sieve that divided by all known 16-bit primes (this table was produced using the Sieve of Eratosthenes), followed by the Fermat test.