Closed devkil closed 1 year ago
Hi, This is over 2 years old so I am guessing answering now would be a bit late. Sorry that it seams ot have gone unanswered previously. If this is still relevant then please reopen and we can attempt to answer the questions.
Hello, I student learning about SRTP and have an assignment to study the application of SRTP on a softphone linphone. But I have a few things to ask.
Generate Round Key
from that function,
srtp_kdf_init ()
function callsrtp_aes_icm_context_init
where in one of the stages it makes around key
for the aes process with functionsrtp_aes_expand_encryption_key(key, base_key_len, &c->expanded_key)
. The parameter used in this function is akey
derived fromtemp_key
in the srtp.c. Is it true that the round key is generated from the master key instead of the session key?In aes counter mode, the
input aes
process iskeystream suffix
, which is built fromnonce and counter
values. This keysream suffix value is generated from the process of calling the functionsrtp_cipher_set_iv -> srtp_aes_cm_set_iv
. This value will then be performed bitwise XOR with RTP Packet payload to produce ciphertext that is ready to be sent. Then which variable holds the RTP Packet?Encryption using AES ICM the encryption process is done through the function
For each function call, if the AES_CM_128 crypto suites configuration is used, is it done for each data packet or for all data packet in the RTP stream? What is the size of the payload buffer that encrypted by srtp_aes_icm_encrypt ? How about the maximum size of the payload can be encrypted ?
Best Regards,