RSA Cheat Sheet

Setup

• n = p * q
• m = (p - 1) * (q - 1)

Choose e

• smallest number > 1 that does NOT divide m

Find d

• find d such that: (e * d) % m = 1

Encryption

• c = (message ^ e) % n

Decryption

• message = (c ^ d) % n

Key Reminders

• always reduce early using % n
• break big exponents into smaller ones
• always check: (e * d) % m = 1
• decrypted message should match original