Vigenère Cipher: Encrypt and Decrypt Text with a Key
The Vigenère Cipher encrypts or decrypts text by applying shifts from a repeating keyword. Each key letter maps to a number (A=0, B=1, and so on) and shifts the corresponding plaintext letter. Non-letter characters pass through unchanged and do not advance the key. It is useful for learning classical cryptography, but it is not secure by modern standards.
The Vigenère Cipher is a browser-based tool for encrypting and decrypting text with a repeating keyword. It applies a different letter shift according to the current key letter, making it a useful way to explore a well-known classical cipher. The method was once called “le chiffre indéchiffrable,” but it is not secure by modern standards.
For each plaintext letter, the corresponding key letter determines the shift: A maps to 0, B maps to 1, and the sequence continues in the same way. The keyword repeats as the text is processed. Non-letter characters pass through unchanged and do not advance the key, so spaces and punctuation do not alter which key letter is used for the next letter. The tool’s steps also refer to a key or salt and to algorithm and option controls; specific option names are not described here.
Plaintext is readable text before encryption, while ciphertext is the transformed result. Converting between them can help with learning, checking a cipher exercise, or working with a message when you have the appropriate key. Unlike modern cryptographic systems, the Vigenère cipher should not be used to protect sensitive information.
The Vigenère Cipher runs entirely in your browser: your input is processed on your device and is not uploaded, stored, or sent to a server. It works offline after the page has loaded, so you can continue using it without a connection.
This tool can help developers, DevOps engineers, students, and anyone exploring classical cryptography. You can try a known input, inspect how the key changes each letter shift, and copy the resulting text without sending your content to a server.
Step 1: Enter or paste the text you want to process. You can also drop your content into the tool.
Step 2: Enter the requested key or salt. The Vigenère cipher uses a repeating keyword to determine each letter shift.
Step 3: Choose the cipher operation and any available algorithm or option settings. The input identifies these controls but does not specify individual options.
Step 4: Run the operation and review the result. Letter shifts depend on the key, while non-letters pass through without advancing it.
Step 5: Copy the output for your notes, exercise, or other local use.
Use case: Check a Vigenère cipher result against text you were given. Comparing the output locally can help you spot a key or input mismatch.
Use case: Learn how a classical cipher behaves by trying known text with different keys. The letter-by-letter shifts make the repeating-key method easier to explore.
Use case: Process text locally instead of handing it to a third-party page. The tool runs in your browser and does not send your input to a server.
Use case: Work through a classroom or self-study exercise on classical cryptography. Encrypting and decrypting sample text helps demonstrate how a repeating key affects letters.
Use case: Decode a Vigenère-encrypted message when you have the relevant key. The tool can apply the cipher in reverse to recover the plaintext.
Use case: Experiment with how punctuation and spaces behave during encryption or decryption. Non-letter characters pass through and do not advance the key.