I've been reading up on Codecs. Motorola has the MC145505 PCM Codec which samples at 8khz and the PCM output is at 64kbps. We can then use the MC145532 ADPCM Transcoder to reduce the data stream to 16kbps. With the breaks in spoken languages, perhaps we could get this to compress just enough to go through a 14.4 kbps modem.
How about just feeding the 16kbps stream to either a DES chip or a microcontroller programmed for IDEA encryption/decryption? And don't even bother with 14.4. Zyxel modems can do 16.8 & 19.2kbps full duplex. But Zyxel's modulation is proprietary. A new standard called v.32terbo has emerged which standardizes 16.8 and 19.2 modulation - I believe some of AT&T's new modems support v.32terbo. Down the road a bit 21.6, 24.4 & 28.8 modulation (v.FAST) will be more common. The way I see it, the hassle of squeezing 16kbps into a 14.4kbps bandwidth pipe is not worth the agrivation when you can pipe it straight into a Zyxel or v.32terbo modem right now.
Anyway, who knows of a DES or RSA chip which will do 16kbps?
They all do, some chips even go as high as several megabits per second for DES. I don't know of any chips that do RSA though.
Then all we need is a microcontroller to run the show, and perform D-H or RSA key exchange.
Exactly. --- thug@phantom.com