Wednesday, May 02, 2007

BCR Comments on CALEA

This was taken from a post at BCR by David Passmore :
CALEA doesn’t apply to ISP storage of email, Web hosting or DNS lookup—only switching and transmission. But switching potentially includes both routers and softswitches for voice.

There is a standard for CALEA lawful intercept—ANSI-J-STD-025-A—but it’s principally for circuit-switched PSTN calls, and lacks any guidance for intercepting VOIP. In the Internet world, there’s RFC 3924, “Cisco Architecture for Lawful Intercept.” However this isn’t a standard; it just presents some of the important concepts.

CALEA requires collection of both intercept-related-information (e.g., source/destination phone numbers, duration of phone calls, etc.) and the contents of the call itself. With VOIP, this might mean that an ISP must deliver RTP packets carrying digitized voice regardless of what codec is used. Similarly, call control information might require the collection and delivery of SIP, Skypeor other signaling packets to law enforcement.

How these packets are to be transmitted to law enforcement is unknown, as is the question of who will pay for the WAN needed to carry intercept requests and responses (this may be another unfunded mandate). Can the Internet be used for this purpose (assuming suitable encryption)? How will the FBI or other law enforcement agencies handle the large number of WAN connections from ISPs and colleges?

Under CALEA, decryption of intercepted call contents or signaling packets is the responsibility of law enforcement; the ISP only has to deliver copies of these encrypted packets. But what about unencrypted VOIP? Does the ISP have to convert media back to voice before delivery to law enforcement, or just send the VOIP packets and signaling information? But even this latter approach is problematic, since ISP routers don’t know anything about phone calls; IP routers don’t decode voice packets or track call state, so how can they intercept particular VOIP calls?

More here.

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