Gronsfeld Cipher client-side
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How to use Gronsfeld Cipher

The Gronsfeld cipher is a variant of the Vigenère cipher where the key is a sequence of digits instead of a word. Each digit (0 to 9) gives the shift to apply to the matching letter of the text, and the key repeats across the whole message. Enter a numeric key to encrypt or decrypt. Like Vigenère, it's a historical polyalphabetic cipher, processed client-side.

Vigenère variant with a numeric key.

GronsfeldVigenèrePoly-alphabétiqueCryptographie

How to use Gronsfeld Cipher

The Gronsfeld cipher is a variant of the Vigenère cipher where the key is a sequence of digits instead of a word. Each digit (0 to 9) gives the shift to apply to the matching letter of the text, and the key repeats across the whole message. Enter a numeric key to encrypt or decrypt. Like Vigenère, it's a historical polyalphabetic cipher, processed client-side.

Frequently asked questions

How is it different from Vigenère?

The key is numeric (0–9) instead of a word. Each digit gives the shift directly, whereas Vigenère first converts the key's letters into shifts.

Can shifts exceed 9?

No, each key digit gives a shift of 0 to 9. For larger, more varied shifts use Vigenère instead.