Vigenère Cipher
Calculate Vigenère Cipher instantly with the exact formula and a worked example.
Vigenère Cipher
Ciphertext index of coincidence
Ciphertext lengthchars
Key length
3.8352chars
Likely key length
4
Possible keys of that length
4.57e+5
More about: Vigenère Cipher
What it calculates
The “Vigenère Cipher” calculator computes Key length in chars from 2 parameters: ciphertext index of coincidence, ciphertext length (chars).
Standard IT calculations for developers and sysadmins.
Example calculation
With parameters Ciphertext index of coincidence = 0.045, Ciphertext length = 500 chars the result is 3.84 chars (Estimate for English text (IC ≈ 0.065); refine with the Kasiski method).
How to use
- Enter ciphertext index of coincidence and ciphertext length — each field above is adjustable with a slider.
- Key length (chars) is calculated automatically as you type.
- Check the worked example below to see the formula applied to real numbers.
- Copy the result or bookmark this calculator.
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FAQ
How is Vigenère Cipher calculated?
The Vigenère Cipher calculator computes Key length (in chars) from ciphertext index of coincidence, ciphertext length. Enter your values above and the exact formula is applied instantly; a worked example with real numbers is shown below.
Is the Vigenère Cipher calculator free?
Yes. It is completely free, needs no signup, runs entirely in your browser, and sends no data to any server.
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