How to Solve the Base64 Cipher

These aren't really secret. They're the ways machines and devices spell — binary, hex, Base64, phone keypads, keyboards, and the Enigma machine — and they turn up in puzzle hunts because they look impenetrable until you know the trick.

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How to recognise it

Only 0s and 1s is binary. Pairs of 0–9 and A–F is hex. A jumble of upper and lower case that ends in = is Base64. Runs of the same digit are a phone keypad, and text full of neighbouring keys is a keyboard slip.

Base64 The encoding email attachments travel in. Every 4 characters hold 3 bytes; an = at the end is padding.

A worked example

Nothing here is secret — it's how a machine spells. Recognise the encoding and you can read it straight back. This one is Base64. The key: Base64. The encoding email attachments travel in. Every 4 characters hold 3 bytes; an = at the end is padding. Convert the first three characters back and they read T R E. The answer was TREASURE MAP.

Working one out from scratch

Name the encoding and the rest is lookup. Do the first few characters by hand so you're sure of the format, then let a converter do the remaining ones — that's what they're for.