Hide messages using playing cards – cryptographic steganography
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There are 52! different ways to shuffle a pack/deck of 52 playing cards – over 80 unvigintillion permutations (8×1067).
That's equivalent to 225 bits, which could be used to represent any message consisting of 28 8-bit characters.  However, there are countless ways of encoding a message – so by compressing the text before turning it into the corresponding sequence of playing cards, it's possible to handle longer messages (in English, at least).  If you allow cards to face both up and down, then messages can be just over 20% longer (277 bits, or 34 8-bit characters with 363 sexvigintillion permutations – 3.6×1083).  When decoding, try using the Reverse and Flip all buttons if you think you may have entered the sequence the wrong way.

With this encoder, you can use any Unicode character – i.e. digits, punctuation, mixed case letters and non-English symbols, for example with accents/umlats, characters from Chinese, Japanese, Korean, etc., and even random things like smiley faces.  Short messages require fewer cards, so there's no need to use a whole pack (you might use a "Joker" to mark the end).  If you want to use multiple packs for longer messages, simply encode each part of your message using one pack at a time.  See this technical document to learn more.  This web page does not steal / transmit what you type.
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Please select each card in the correct sequence

© 2014 by Lee J Haywood (GPL licence)