Tool to decrypt/encrypt with T9 mode for SMS messages on mobile phone. T9 (Text on 9 keys) is a predictive text method based on a dictionary, used in mobile phones to type text on a keyboard with only numeric keys
T9 (Text Message) - dCode
Tag(s) : Telecom, Substitution Cipher
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T9 mode should not be confused with Multitap ABC mode. 'DCODE' is written as '32633' in T9 but '3222666333' in Multitap.
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
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.