Tool to decrypt/encrypt with T9 mode (predictive) for SMS text messages for (old) mobile phones or numeric keypads.
T9 (Text Message) - dCode
Tag(s) : Telecom, Substitution Cipher
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T9 (Text Message)
T9 Decoder/Phonewords Finder
T9 vs Multitap Confusion
T9 mode should not be confused with Multitap ABC mode. 'DCODE' is written as '32633' in T9 but '3222666333' in Multitap.
T9 Encoder
Textonym list
Answers to Questions (FAQ)
What is T9? (Definition)
T9 (Text on 9 keys) is a predictive text method based on a dictionary, used in (old) mobile phones to type text on a keyboard/keypad with only numeric keys
How to encrypt using T9 cipher?
T9 encryption replaces a letter by the corresponding key code on a mobile phone keypad/keyboard (compatible with Text on 9 keys).
Example: DCODE becomes 32633 on a T9 keyboard
Do not confuse the T9 with the multi-tap code (successively press the keys until you get the correct letter)
How to decrypt T9 cipher?
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.
How to recognize T9 ciphertext?
The ciphered message is made of digits, if there are 1 or 0, these digits can only code spaces or punctuation.
The T9 had other proprietary trade names like iTap, XT9, LetterWise or WordWise.
The notions of SMS writing/language or texting or autocorrect are clues as well as old mobile phones like Nokia 3210.
What are the variants of the T9 cipher?
Mobile phones have other typing techniques (not predictive), such as Multitap code (ABC mode). With the same keyboard, DCODE is written 3222666333.
What is a Textonym?
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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When was T9 invented?
The T9 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.
Source code
dCode retains ownership of the "T9 (Text Message)" source code. Except explicit open source licence (indicated Creative Commons / free), the "T9 (Text Message)" algorithm, the applet or snippet (converter, solver, encryption / decryption, encoding / decoding, ciphering / deciphering, translator), or the "T9 (Text Message)" functions (calculate, convert, solve, decrypt / encrypt, decipher / cipher, decode / encode, translate) written in any informatic language (Python, Java, PHP, C#, Javascript, Matlab, etc.) and all data download, script, or API access for "T9 (Text Message)" are not public, same for offline use on PC, mobile, tablet, iPhone or Android app!
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Cite as source (bibliography):
T9 (Text Message) on dCode.fr [online website], retrieved on 2023-02-08,
