PDU SMS Sender Number Extraction

You're working with raw GSM SIM filesystem data, and that looks like a raw PDU-encoded SMS message. Let's parse it and extract the sender's phone number.

🔍 Step-by-step PDU Analysis:

PDU string:

0307913366003000F011000B9115132893723F0000AA205530306B58305977636A4E756379466A4A46387863313941647A4E7A4D47316C

The format for a PDU SMS typically is:

css

[SMSC info length][SMSC info][PDU type][TP-MR][TP-DA length][TP-DA (receiver)][TP-PID][TP-DCS][TP-SCTS][TP-UDL][TP-UD]

But in your case, the PDU starts with:

r

03 07 91 33 66 00 30 00 F0 11 00 0B 91 15 13 28 93 72 3F ...

We'll parse it accordingly.

🔧 Breakdown of the important fields:

• SMSC Length (in octets):
  03 → means 3 bytes for SMSC info follow.

• SMSC Info (3 bytes):
  07 91 33
  → 07 = SMSC length again? Maybe an error or part of the SMSC. Let's treat it as:SMSC address:

• 91 → international format

• 33 66 00 → swapped semi-octets: 336600 → becomes +336600 (or likely something wrong here – not critical now)

• PDU Type (1 byte):
  30 → typical SMS-DELIVER PDU

• Message Reference (MR):
  00

• Sender Address Length:
  0B = 11 digits

• Sender Address Type-of-Address (TOA):
  91 → international number

• Sender Address Value:
  15 13 28 93 72 3F
  This is in semi-octet swapped format. We decode it:

• 15 → 51

• 13 → 31

• 28 → 82

• 93 → 39

• 72 → 27

• 3F → F3 → drop the F Resulting digits: 51318239273
  With the + from 91, the sender's number is:

✅ Sender Number: +51318239273

If you want a Python script to extract this kind of info automatically, let me know!