xLen intended length in octets of the output octet string
Output: X octet string of length xLen
Operation: 1. Let xLen be the intended length in octets of the output octet string X.
Copyright © 2002 RSA Security Inc.
PKCS #1 V2.1: RSA CRYPTOGRAPHY STANDARD (June 14, 2002) 9
2. If x ≥ 256xLen, output "integer too large" and stop.
3. Let X be the empty octet string.
4. For i from xLen - 1 down to 0, do:
a. Let xi be the least significant