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For K-12 Students · RSA Encryption

RSA Encryption for a key exchange

Built for k-12 students learning it in middle or high school. Watch the idea come alive with plain-language steps and everyday examples — perfect for projects and homework. Simulate a key exchange live below — adjust the inputs and watch it respond, right in your browser.

RSA Public-Key EncryptionLive

the math behind secure internet

message

↓ encrypt: 42^3 mod 391

ciphertext

189

↓ decrypt: 189^235 mod 391

recovered

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.

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Data Inspector

Modulus n = p·q391

φ(n)352

Public key e3

Private key d235

Governing equation

n = pq = 17 \cdot 23 = 391, c = m^{e} mod n = 189, m = c^{d} mod n = 42

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.

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Frequently asked questions

Is this good for k-12 students?: Yes — this version of "RSA Encryption for a key exchange" is framed for k-12 students learning it in middle or high school. Watch the idea come alive with plain-language steps and everyday examples — perfect for projects and homework.
Do I need to install anything?: No. It runs in any modern browser, free, with no account required.