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RSA Decryption (mod n) Calculator

m = c^d mod n — textbook RSA decryption for small keys.

Decrypts an RSA ciphertext by computing m = c^d mod n. Intended for educational toy key sizes (small c, d, n); large keys require bigint modular exponentiation.

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Daniel Oh By Daniel Oh
Published Last reviewed 1 min read

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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

m = c^d mod n (toy keys only)

In depth

Decrypts an RSA ciphertext by computing m = c^d mod n. Intended for educational toy key sizes (small c, d, n); large keys require bigint modular exponentiation.