Covert Mail: Morse & Ciphers

Learn Morse code the way radio operators do, crack the ciphers people really used, then send a coded message of your own.

Covert Mail is a field desk of secret codes. Each code is a dossier: read its history, practice it a few characters at a time, then decode a real message to file it in your archive.

MORSE CODE, BY EAR
• The Koch method: every character at full speed from the first lesson, two at a time, so you hear each one as a single sound instead of counting dots
• Farnsworth spacing: characters at your chosen speed with extra room between them while you learn
• Tones made on your phone at any speed and pitch, with an on-screen signal lamp and optional vibration
• Decode SOS and Samuel Morse's first message, "What hath God wrought"

SEND IT ON A BRASS KEY
Hold the on-screen key to send. Keying missions teach every letter from A to Z, and the results show your marks against the ideal timing, so you can see where your rhythm drifted. The last one has you key the Titanic's call: "Come at once. We have struck a berg."

FIFTEEN DOSSIERS
Morse code, the NATO phonetic alphabet, the Caesar shift, Atbash, tap code, pigpen, Braille, the Polybius square, flag semaphore, a keyword cipher, Vigenère, the rail fence, ROT13, a substitution cipher and a book cipher. Each comes with its history: Caesar's shift of three, the tap code American prisoners used through the walls of Hỏa Lò, Polybius signaling with torches, Louis Braille's six dots.

Your handler, Harriet Vale, leaves a note as you open each dossier. Every dossier you clear turns up one word of a letter the desk's founder cut into fifteen pieces.

PRACTICE THAT KNOWS WHAT YOU MISS
Practice batches are planned around the characters you get wrong, and a miss comes back a few clues later until it sticks. A new intercept arrives every day, the same for everyone, and an optional daily reminder tells you when it is in.

THE CIPHER DESK
A Morse code translator and cipher decoder in one. Encode or decode anything in fifteen codes, including a random substitution alphabet and a book cipher with any book you choose. Play Morse aloud, flash it on your phone's torch, or key it in yourself. Then send a coded message to a friend through any messaging app, with or without the key. Friends without the app can open it in their browser.

ON YOUR WRIST
On Apple Watch, Covert Mail taps Morse on your wrist: a light tick for a dot, a heavier tap for a dash. Pick the letter from four and build a streak, or key Morse back by tapping the watch face. Today's letter can sit on your watch face as a complication. The watch app also works without your phone, offline, with no ads.

No account. Your progress stays on your phone. Classical codes only: these are for learning and fun, not for protecting real secrets.

Covert Mail first came to the App Store in 2009. This is the rebuilt version.