Caesar / ROT
Shifts every A–Z letter by a fixed integer; the same shift is subtracted to decode. Only 25 non-zero shifts exist, so it falls to brute force instantly.
01 Console
Ready.
02 Text
Input: 0 letters · Output: 0 letters
03 Frequency scope
Live A–Z letter counts. Substitution ciphers shift the profile; transposition keeps it.
04 Caesar crack
All 25 decode shifts for the current input.
05 Field notes
Vigenere
Repeats an alphabetic key across the message, with each key letter supplying a Caesar shift. Non-letters pass through and do not advance the key here.
Rail Fence
A transposition cipher: characters zigzag across rails and are read row by row. It moves positions instead of substituting letters, so the frequency profile is unchanged.
Atbash
Maps A→Z, B→Y, and so on. It has no key and is reciprocal, so applying it a second time returns the original text.
! These ciphers are toys for learning, puzzles and history. They are not suitable for protecting sensitive data.