T9 (Text Message)

T9 encryption replaces a letter by the corresponding key code on a mobile phone keypad (compatible with Text on 9 keys).

Example: DCODE becomes 32633

Do not confuse the T9 with the multi-tap code (successively press the keys until you get the correct letter)

The decryption of the T9 is normally based on a dictionary where all the words have been previously encoded.

It is normally impossible to write a word that does not exist but the dCode T9 translator in brute-force mode will test all the possibilities of words.

Example: 22 = AA,AB,AC,BA,BB,BC,CA,CB,CC

This functionality allows creating or remembering phonewords for phone numbers avoiding digits 0 and 1.

The ciphered message is made of digits, if there are 1 or 0, these digits can only code spaces or punctuation.

Mobile phones have other typing techniques (not predictive), such as Multi-tap code (ABC mode). With the same keyboard, DCODE is written 3222666333.

The T9 has proprietary versions like the XT9, the LetterWise ou the WordWise.

A textonym is the name given to each word written in the same manner in T9. Textonym list

Example: COOL = 2665 = BOOK

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Patent is from 1985. The T9 was popularized with SMS texting on the first old compatible GSM phones (late 90s, early 2000), but today, with smartphones/iphones and their tactile interfaces and their complete keyboard, the T9 is disappearing but it can still be used to easily code secret messages.