A=0
This is close to the Vigenère convention: A is 0, B is 1, C is 2. A in the key therefore applies no shift.
Keyword shift
Test a repeated alphabet shift with A=0, A=1, or a number sequence.
Codes
Encode or decode a message with a keyword turned into shifts. Compare A=0 and A=1, view the key values, and check the first applied shifts.
Settings
Conversion direction
Key type
Letter values
The key repeats only over letters. Spaces, digits, and punctuation stay in place.
Source text
0 source char.
Result
Add source text.
Key values
—
First shifts preview
LetterKeyShiftResult
Quick explanation
Enter text, choose encode or decode, then add a keyword. The tool repeats the key shifts over the message letters and displays the values used. Number sequence mode lets you test known shifts directly.
Try this too
Need classic Vigenère?
Use the Vigenère cipher tool if your message follows the usual A=0 convention without another variant to test.
Additional information
What is a keyword shift?
A keyword shift applies a repeated sequence of shifts to the letters of a message. The keyword is converted into numbers, then each number shifts the matching letter.
A=1
This convention is common in alphabet puzzles: A is 1, B is 2, C is 3. It gives another lead to test.
Number sequence
If you already know the shifts, enter a sequence directly, such as 12,14,14,13.
Example with MOON
| Convention | M | O | O | N |
|---|---|---|---|---|
| A=0 | 12 | 14 | 14 | 13 |
| A=1 | 13 | 15 | 15 | 14 |
Compared with Vigenère
Vigenère usually uses A=0. This tool makes the convention visible and lets you compare A=0, A=1, or a raw number sequence.
Compared with Caesar
Caesar uses one fixed shift for the whole text. Here, the shift changes according to the repeated key.
Related tools
Try the Vigenère cipher or the Caesar cipher.
In the shift family
For a very simple fixed shift, also try ROT13. For a freely chosen fixed shift, use the Caesar cipher.
Limits and reuse
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