The two large numbers are passed to dc.
All further processing is done by dc.
5- Take one of the large numbers, increment it such that it is always congruent to 2 modulo the public exponent. If not prime, goto step 5. Repeat steps 5 and 6 with the other large number to generate the second prime. Search the coderpunks archives for a message from Ron Rivest to me for the details. The above is all from memory.