Mobile Cipher
The Mobile Cipher lets you write messages using old-school mobile keypad codes. On old mobile phones (before smartphones), you had to press number keys multiple times to type letters. Each number key had 3-4 letters assigned to it.
A classic telephone keypad layout used for T9-style encoding. Source: Wikipedia
Encoding
To encode a message, find each letter on the keypad and write down the key number repeated by how many times you'd need to press it.
- H → Press key 4 twice →
44 - E → Press key 3 twice →
33 - L → Press key 5 three times →
555 - O → Press key 6 three times →
666 - Space → Press key 1 once →
1
So "HELLO WORLD" becomes a series of number presses like you'd make on an old phone!
Decoding
To decode, group the numbers and convert each group back to its corresponding letter:
- Split the encoded message into groups of the same digit
- Count how many times each digit repeats
- Look up which letter that combination represents
Example:
Input: HELLO WORLD
Encoded: 44 33 555 555 666 1 9 666 777 555 3
Decoded: hello world
The decoder figures out that 44 means the 2nd letter on key 4 (which is H), 33 means the 2nd letter on key 3 (which is E), and so on!