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Re: [Sip] media-security-requirements and lawful intercept

To paraphrase Tim / 33.106, the entities are only required to provide decryption in the following cases:

1. The encryption was provided by NWOs/APs/SvPs AND the NWOs/APs/SvPs possesses the information necessary to decrypt the communication.

2. NWOs/APs/SvPs provides the encryption keys but does not provide the encryption itself

It seems like neither of these is necessarily the case when the endpoints use an end-to-end secure key negotiation mechanism: Since the endpoints are agreeing on keys between themselves, you're never in case (2). With regard to case (1), even if the provider builds the encryption system into the terminal, without some additional key disclosure mechanism, they won't have the information necessary to decrypt the communication.

So it doesn't seem like there's any technical issue at all, based on this requirement. The service provider is just required to provide access to what he has access to, even if that's just encrypted traffic with no keys.

--Richard




Dan Wing wrote:
...
1. It's not clear to me that people are correctly parsing LI
requirements. I'm not an expert on CALEA, let alone laws in other
countries, but it's not my understanding that there is any
regulatory requirement that forces carriers of voice or data
traffic to arrange for disclosure of plaintext when they don't have
the keys. I.e., if I buy data service from Comcast and choose to
run a VPN, there is no requirement that Comcast somehow obtain the
keys to deliver them to the FBI.

It's less clear to me what the requirements are for 3G-style
carriers when the endpoints are doing the crypto. I.e., I'm quite
certain that if AT&T terminates the crypto they need to provide the
plaintext on request, but a lot less certain that they need to
provide the plaintext if the crypto is end-to-end.
Timothy Dwight posted a followup on 3GPP's requirement that should
be helpful on those points. What remains unsaid in that quoted text is crypto performed by the endpoint itself (as with DTLS-SRTP).

Tim mentioned to me privately that his posting to SIP is being held up; here is the content:

    From: Dwight, Timothy M (Tim) <timothy.dwight at verizonbusiness.com>
    To: Eric Rescorla; Dan Wing
    Cc: IETF SIP List
    Subject: RE: [Sip] media-security-requirements and lawful intercept

    On point #1, 3GPP 33.106 says under "Security of Processes":

    "NWOs/APs/SvPs shall not be responsible for decrypting, or
    ensuring the LEA's ability to decrypt, any communication
    encrypted by a subscriber or customer, unless the encryption
    was provided by the NWOs/APs/SvPs and the NWOs/APs/SvPs
    possesses the information necessary to decrypt the
    communication or the NWOs/ APs/SvPs provides encryption keys
    but does not provide the encryption itself. In the case that
    the NWOs/ APs/SvPs provides encryption keys to the subscriber
    or customer but does not provide the encryption itself, the
    NWOs/ APs/SvPs shall provide the keys to the LEA if required
    by national regulations."

    The same text is found in ETSI TISPAN TS 133 106.

    tim

-d


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_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use sip-implementors at cs.columbia.edu for questions on current sip
Use sipping at ietf.org for new developments on the application of sip