I still haven't been able to find the particular documentation around class 2 SMS verification. Most of the things I'm finding talk about IMSI using HMAC-SHA1 f

I still haven't been able to find the particular documentation around class 2 SMS verification. Most of the things I'm finding talk about IMSI using HMAC-SHA1 for OTA validation. Is this at a lower level? Edit: Found this: http://www.3gpp.org/ftp/tsg_sa/wg3_security/TSGS3_33_Beijing/Docs/PDF/S3-040242.pdf http://www.3gpp.org/ftp/tsg_sa/wg3_security/TSGS3_33_Beijing...