Text Encryption & Encoding

Every method here is either a classical cipher or a reversible text encoding, all implemented in plain JavaScript that runs in your browser. None of them provide real cryptographic security, and each carries a security label in the tool (Encoding, Weak, or Moderate) to make that clear.

The substitution ciphers shift or swap letters within the A-Z alphabet and leave other characters untouched. Caesar shifts every letter by a fixed amount you choose (1 to 25); ROT13 is just Caesar with a shift of 13, which is its own inverse. Atbash mirrors the alphabet (A maps to Z, B to Y) and needs no key. The Affine cipher applies the formula (a * x + b) mod 26, where key A must be coprime with 26 (the tool restricts A to 1, 3, 5, 7, 9, 11, 15, 17, 19, 21, 23, 25 so a modular inverse exists for decryption). Vigenere is a polyalphabetic cipher that shifts each letter by a different amount derived from a repeating keyword, which hides the simple letter-frequency signature that breaks Caesar - but it falls to Kasiski examination and index-of-coincidence analysis once the key length is found.

The Rail Fence cipher is a transposition cipher: it writes your text in a zigzag across a chosen number of rails (2 to 10) and reads it back off row by row, rearranging letters without changing them. The XOR cipher combines each character code with a repeating key byte using bitwise XOR, which is symmetric (applying it twice with the same key restores the original). The remaining methods are encodings, not ciphers at all: Base64, Hexadecimal, and Binary re-express the bytes of your text in another representation, and Morse maps letters to dots and dashes. Anyone can reverse an encoding instantly without a key, so they offer zero secrecy - they are useful for transport, display, or learning, not protection.