RSA encryption
RSA with small primes, so every number stays readable. The public exponent is fixed at e = 65,537, the value used in practice. Pick two primes to generate a key pair, then pick a message and watch it encrypt with the public key and decrypt with the private key.
An adjustable RSA example with a fixed public exponent of 65,537, with notes explaining that the totient is computed from each prime minus one and that the private exponent is derived from the totient.
Step 1 · choose two different primes
Modulus
The modulus is the product of the two primes and is made public.
Totient
φ = (p − 1) × (q − 1)
Exponents
Public key · shared
Private key · secret
Step 2 · choose a message
Step 3 · encrypt with the public key
Step 4 · decrypt with the private key