On Thu, Jun 18, 2020 at 09:46:52AM +0200, Ronny Meeus wrote: > I added the print function and the result of the print is as follows: > probable_prime BN_num_bits 1473 1536 The difference is exactly 63 bits! Suggesting that either the high 64-bit bit word is 0x0000000000000001 or the bit counting is not working right. What is the "endianness" of this CPU? Is it big-endian or little-endian? And does OpenSSL expect the correct one? -- Viktor.