Encrypt / decrypt text

Encryption turns readable text (plaintext) into unreadable ciphertext that can only be reversed with the correct key. This tool encrypts and decrypts text with several symmetric ciphers, where the same secret key is used for both directions. It is useful for learning, testing interoperability and protecting short notes.

How to use it

1. Choose the algorithm.
2. Enter the text and a secret key or passphrase.
3. Encrypt to get the ciphertext, or paste ciphertext and the same key to decrypt.

The algorithms

• AES: the Advanced Encryption Standard, used by governments, TLS, disk encryption and Wi-Fi. This is the one to use.
• TripleDES: applies the old DES cipher three times. Deprecated by NIST and slow; only for legacy compatibility.
• Rabbit: a fast stream cipher from the eSTREAM project, little used in practice.
• RC4: a stream cipher with known weaknesses, banned from TLS. Do not use it to protect real data.

How passphrases become keys

When you type a passphrase, it is converted into a key and a random salt is included in the output, which is why the same text and passphrase give a different ciphertext each time. The output is commonly in the OpenSSL-compatible format starting with U2FsdGVkX1, which is Base64 for Salted__.

Security guidance

• Use AES with a long, random passphrase. Short or dictionary passphrases can be brute-forced.
• Encryption alone does not prove the data was not modified; modern systems use authenticated modes like AES-GCM.
• Share the key through a different channel than the ciphertext.
• For files and messages between people, established tools like PGP or age are better choices.

Encryption and decryption run locally; your text and key are not sent anywhere.