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Ask HN: How does this bank delete a sent SMS?

5 points by laurensr 4y ago

fIREpOK 4y ago
Not sure but they don't automatically delete any of my SMS (pin codes or not) here in the US
laurensr 4y ago
This Belgian bank sends new pin codes by SMS. Phones delete them after 2 days. How is this achieved?
- nulbyte 4y ago
  They may be dumbing down their explanation of the validity period during which a mobile device can receive the message. If a text message can't be delivered, because the device cannot be reached (e.g., it's off or out of the coverage area), the message center holds the message. However, you can set a validity period, after which undelivered messages are supposed to be deleted. Some carriers here in the U.S., however, don't respect that validity period, so there's really no guarantee. Other than that, I don't think there is a supported way to delete a message that has been received, unless the text message is sent some other way; maybe other apps, like iMessage, WhatsApp, etc., support this?
t8sr 4y ago
You send a second SMS with the same PID and it’ll overwrite the first one. It’s in the GSM standard and described on Wikipedia: https://en.wikipedia.org/wiki/GSM_03.40 https://en.wikipedia.org/wiki/GSM_03.40
- 082349872349872 4y ago
  Did you mean the TP-MN (and TP-RD) fields by "same PID"?
  - nulbyte 4y ago
    Looks like there is a TP-PID field that has values to indicate replace message: https://security.stackexchange.com/questions/19731/how-does-a-new-sms-message-overwrite-a-previous-one https://security.stackexchange.com/questions/19731/how-does-... I find this fascinating; I didn't know this functionality existed.
    - 082349872349872 4y ago
      Aha, not "same PID", but "special PID": https://en.wikipedia.org/wiki/GSM_03.40#Protocol_Identifier https://en.wikipedia.org/wiki/GSM_03.40#Protocol_Identifier (65-71) also potentially interesting: is there a no-notification ping? Sometimes I am glad I grew up in the fixed-line era. > Short Message Type 0 is known as a silent SMS. Any handset must be able to receive such short message irrespective of whether there is memory available in the (U)SIM or ME or not, must acknowledge receipt of the message, but must not indicate its receipt to the user and must discard its contents, so the message will not be stored in the (U)SIM or ME.

5 points by laurensr 4y ago

fIREpOK 4y ago

Not sure but they don't automatically delete any of my SMS (pin codes or not) here in the US

laurensr 4y ago

This Belgian bank sends new pin codes by SMS. Phones delete them after 2 days. How is this achieved?

nulbyte 4y ago
They may be dumbing down their explanation of the validity period during which a mobile device can receive the message. If a text message can't be delivered, because the device cannot be reached (e.g., it's off or out of the coverage area), the message center holds the message. However, you can set a validity period, after which undelivered messages are supposed to be deleted. Some carriers here in the U.S., however, don't respect that validity period, so there's really no guarantee. Other than that, I don't think there is a supported way to delete a message that has been received, unless the text message is sent some other way; maybe other apps, like iMessage, WhatsApp, etc., support this?

t8sr 4y ago

You send a second SMS with the same PID and it’ll overwrite the first one. It’s in the GSM standard and described on Wikipedia: https://en.wikipedia.org/wiki/GSM_03.40 https://en.wikipedia.org/wiki/GSM_03.40

082349872349872 4y ago
Did you mean the TP-MN (and TP-RD) fields by "same PID"?
- nulbyte 4y ago
  Looks like there is a TP-PID field that has values to indicate replace message: https://security.stackexchange.com/questions/19731/how-does-a-new-sms-message-overwrite-a-previous-one https://security.stackexchange.com/questions/19731/how-does-... I find this fascinating; I didn't know this functionality existed.
  - 082349872349872 4y ago
    Aha, not "same PID", but "special PID": https://en.wikipedia.org/wiki/GSM_03.40#Protocol_Identifier https://en.wikipedia.org/wiki/GSM_03.40#Protocol_Identifier (65-71) also potentially interesting: is there a no-notification ping? Sometimes I am glad I grew up in the fixed-line era. > Short Message Type 0 is known as a silent SMS. Any handset must be able to receive such short message irrespective of whether there is memory available in the (U)SIM or ME or not, must acknowledge receipt of the message, but must not indicate its receipt to the user and must discard its contents, so the message will not be stored in the (U)SIM or ME.