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XOR Cipher Output Calculator

Work out xor cipher output instantly with clear inputs, formula shown and shareable results.

About XOR Cipher Output Calculator

XOR is its own inverse, so the same operation encrypts and decrypts. With a random key as long as the message used once, it is a one-time pad and unbreakable; with a short repeating key it is trivially broken, because splitting the ciphertext by key position turns it into several single-byte XOR problems solvable by frequency analysis. XOR is a building block of real ciphers, not a cipher.

Formula

Repeating-key XOR

c_i = p_i XOR k_(i mod m); decryption is the identical operation because XOR is self-inverse

Worked example

With the default values below, XOR Cipher Output Calculator returns Ciphertext (hex) of 477b416371. Change any input above and every figure here is recalculated in your browser.

Inputs used

Plaintext bytes in hex
48656c6c6f
Key bytes in hex
0f1e2d

Results

Ciphertext (hex)
477b416371
Bytes processed
5
Times the key repeats
1.67
Security assessment
Key is shorter than the message, so it repeats and the cipher is breakable by frequency analysis on each key position

Step by step

  1. 1Values used
  2. 2Repeating-key XOR
  3. 3Ciphertext (hex)= 477b416371
  4. 4Bytes processed= 5
  5. 5Times the key repeats= 1.67
  6. 6Security assessment= Key is shorter than the message, so it repeats and the cipher is breakable by frequency analysis on each key position

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is repeating-key XOR so weak?

Bytes at positions congruent modulo the key length share a key byte. Guessing the key length and applying English letter frequency recovers each byte independently.

Where is XOR used legitimately?

Everywhere inside real cryptography — stream ciphers XOR a keystream with the plaintext, and block cipher modes such as CTR and GCM do the same. The security comes from the keystream generator, not the XOR.

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