<html><body><div style="color:#000; background-color:#fff; font-family:arial, helvetica, sans-serif;font-size:10pt"><div><span>Thank you. It's sad because you may have killed a dream. But there is still some hope. Can anyone tell me how did they manage to pull it off</span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: arial, helvetica, sans-serif; background-color: transparent; font-style: normal; "><span><a href="http://www2.rohde-schwarz.com/file_1464/Top-Sec_en.pdf">http://www2.rohde-schwarz.com/file_1464/Top-Sec_en.pdf</a></span></div><div><br></div> <div style="font-family: arial, helvetica, sans-serif; font-size: 10pt; "> <div style="font-family: 'times new roman', 'new york', times, serif; font-size: 12pt; "> <div dir="ltr"> <font size="2" face="Arial"> <hr size="1"> <b><span style="font-weight:bold;">From:</span></b> Benny Amorsen <benny+usenet@amorsen.dk><br> <b><span style="font-weight: bold;">To:</span></b> sab
sab <sabin_098765@yahoo.com> <br><b><span style="font-weight: bold;">Cc:</span></b> Asterisk Developers Mailing List <asterisk-dev@lists.digium.com>; Hans Witvliet <asterisk@a-domani.nl> <br> <b><span style="font-weight: bold;">Sent:</span></b> Saturday, October 27, 2012 2:57 AM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: GSM Encryption<br> </font> </div> <br>
sab sab <<a ymailto="mailto:sabin_098765@yahoo.com" href="mailto:sabin_098765@yahoo.com">sabin_098765@yahoo.com</a>> writes:<br><br>> Thank you for your reply, but I don't want to use a smart phone to do this<br>> or the data connection of the phone. Basically this is were I want to get:<br>> wifi network ->wifi adapter raspberry pi -> asterisk raspberry pi<br>> ("routing")-> ENCRYPTION(personal flavour) ->(chan_mobile)bluetooth<br>> adapter raspberry pi->phone with bluetooth ->voice connection<br>> Can this be done?<br><br>It doesn't look like you have much luck getting people to understand<br>your topology :)<br><br>If I understand you correctly, you have that setup at both ends of the<br>connection, right? And you want to encrypt the voice going through the<br>GSM/whatever network.<br><br>This is possible, but very, very tricky. First of all, if you want<br>encryption you generally cannot handle codec
conversions. You need to<br>send the exact bitstream to the phone that you then expect to see at the<br>other end of the network, so you need to send in exactly the codec used<br>by the GSM network. This codec can change during a call, and you have no<br>way to detect that (other than your decryption suddenly failing). You<br>also have to handle dropped and malformed packets, which is almost<br>impossible.<br><br>I do not believe it is a viable strategy. You could perhaps invent a<br>2400bps modem protocol which would sometimes work over voice-GSM, but<br>the end result would sound awful.<br><br>Ten years ago you could just make a HSCD ("modem") call instead and get<br>57.6kbps through (potentially at the cost of 4 simultaneous calls, but<br>usually less). You may be able to find a provider and phone which still<br>supports that. It gives you a bog-standard serial connection so you can<br>even do PPP and just use SRTP.<br><br><br>/Benny<br><br><br>
</div> </div> </div></body></html>