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My friend sent me the following short message:

D57919749C3641B796384D0795DDE33739ED3E03

How should I decode it?

Hint:

My friend's job is writing software for mobile phones.

Hint2:

The original message was 22 characters long.

Hint 3:

It is relevant that it was a Short Message that my friend sent me.

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  • $\begingroup$ Almost looks like a SHA1 hash.... $\endgroup$
    – Tryth
    Jul 1, 2015 at 11:45
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    $\begingroup$ Clearly, this is simple hex and your friend is trying to tell you "Õytœ6A·–8M•Ýã79í>�" $\endgroup$ Jul 1, 2015 at 11:57
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    $\begingroup$ @Tryth, good thought but it's not a hash. $\endgroup$
    – Vicky
    Jul 1, 2015 at 12:04
  • $\begingroup$ Something to do with mobile phone keypads? $\endgroup$ Jul 1, 2015 at 12:57
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    $\begingroup$ Nope,. not to do with the keypad. $\endgroup$
    – Vicky
    Jul 1, 2015 at 13:06

2 Answers 2

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Your friend sent you text in the form of the 7-bit GSM Alphabet, which is how the text in an SMS message is stored. When decoded, the text will be:

Use GSM 7-bit encoding

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Decoded it is - Use GSM 7-bit encoding

This is the USSD GSM 7bit packed encoding.

I used this tool. Given the original message was 22 characters (above answer) we need to convert the long-form from the question (40 characters) to the SMS (short message service) text.

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