The algorithm that secures the internet, laid bare. Pick two primes, generate a key pair, and watch a message get encrypted and decrypted step by step.
RSA Public-Key EncryptionLive
the math behind secure internet
message
42
↓ encrypt: 42^3 mod 391
ciphertext
189
↓ decrypt: 189^235 mod 391
recovered
42
Controls
Presets
Prime p
Prime q
Message (number < n)
RSA rests on a one-way street: multiplying two big primes is easy, but factoring the product back apart is practically impossible. The public key (n, e) encrypts by raising the message to the power e mod n; only the private key d — computable only from the secret primes — can undo it. Real keys use 600-digit primes; these tiny ones just show the machinery.
Reading this result: The public key (n=391, e=3) turns 42 into ciphertext 189; only the private key d=235, derived from the secret primes, brings it back to 42. With primes this small, n could be factored instantly — real RSA uses 600-digit primes.
Runs locally in your browser — free forever. Scale to the cloud when reality gets heavy.
★ Sign in to save this setupSave your tuned setup, or drop this simulation into your own site, docs, or course page.
How it works
RSA relies on a mathematical one-way street: multiplying two large primes is trivial, but factoring the product is infeasible. The public key encrypts by modular exponentiation; only the private key, derived from the secret primes, can reverse it. This demo uses tiny primes to reveal the machinery — real RSA uses numbers hundreds of digits long.
✦
Ask the AI about this model
The math, the assumptions, real-world uses, or a code translation — explained for this exact simulation.
Is this RSA encryption simulator tool really free?▾
Yes. RSA Public-Key Encryption runs entirely in your browser using your device's own compute, so local use is free forever. You only pay Compute Tokens if you scale a job to the cloud.
Do I need to install anything?▾
No. Everything runs client-side in a modern browser — no downloads, no license, no account required to start.
Can I save or share my simulation?▾
Create a free account to save projects, and use a shareable embed or minted DOI to publish a live, interactive version anywhere.
How accurate are the results?▾
The solver uses established numerical methods, but results are for research and educational purposes and should be validated against experiment or professional review before you rely on them.