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[Linphone-developers] Modified Linphone Encryption

From: Hilman Cino
Subject: [Linphone-developers] Modified Linphone Encryption
Date: Mon, 10 Aug 2020 13:39:23 +0700

hello i want to ask, has anyone ever modified the ortp module on the linphone source?
I am trying to modify a new encryption method that implements the bitwise shift left function which causes the ciphertext to be 2 times larger than the original size (example plaintext 160 bytes, ciphertext 320 bytes) with the following illustration:

Plaintext (in hex): d5d4d3d2d1
d5: 1101 0101 -> (shift left 1) -> 1010 1011 = ab
d4: 1101 0100 -> (shift left 2) -> 0101 0011 = 53
d3: 1101 0011 -> (shift left 3) -> 1001 1110 = 9e
d2: 1101 0010 -> (shift left 4) -> 0010 1101 = 2d
d1: 1101 0001 -> (shift left 5) -> 0011 1010 = 3a

which means d5 shift 1 time to the left, etc The size of shift, place after the ciphertext. So the ciphertext (in hex): ab0153029e032d043a05
When run, only 3 packets can be sent between the phone. On the server, the implementation of this method went well without causing any errors. However, when implemented on linphone, this causes errors such as bus errors, segmentation faults, and so on.
I think this happens due to accessing memory to allocate ciphertext that has not been defined, but when I try to change the code in the ortp file (alloc) or increase the size of the ms_srtp file msgpullup code on the mediastreamer it is still wrong.
Can anyone help me resolve this? Or is there someone who can tell me about the flow in the linphone source code? Or is there someone who understands the code on ortp? It has been almost 1 month for me to have trouble solving this problem and not resolved until now. Please help.
Thank you

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