Tools

FHE Demo

A tiny, educational homomorphic encryption demo using a toy Paillier scheme.

Educational only - not production crypto

This demo uses tiny numbers and a toy Paillier-like setup so you can see homomorphic addition in action. It is not secure and should never be used for real data.

Add two integers without revealing them

Your browser encrypts each value, a simulated server multiplies ciphertexts, and the browser decrypts the sum.

Value A Value B

Ciphertext A

Ciphertext B

Server sum (ciphertext)

Client decrypted sum

Homomorphic addition: the server multiplies ciphertext A and ciphertext B modulo n^2 to produce the ciphertext of (A + B). The browser then decrypts that sum.

How the math works

Encrypt: c = g^m * r^n mod n^2 (m is A or B, r is random so the same input encrypts differently each time).
Combine: c_sum = c_a * c_b mod n^2 (this corresponds to m_a + m_b).
Decrypt: m = L(c^lambda mod n^2) * mu mod n, where L(u) = (u - 1) / n.

Pick values and run the demo.

Toy key parameters

Random tiny primes and derived values used for the demo. These are intentionally small and not secure.

Prime p

Prime q

n = p × q

n^2

Lambda (lcm)

Mu (mod inverse)

Limitations

Uses tiny primes and BigInt math for clarity, not security.
Ciphertexts are much larger than plaintext inputs.
Performance does not scale; real FHE is far heavier.

Security model (30 seconds)

This is a toy Paillier-style construction with tiny primes. It demonstrates homomorphic addition but provides no real security. No server-side secrets and no user tracking are used. Do not use it for production data.