Subject: [pkix] A work item proposal for PKIX WG - A certificate extension to support key escrow in PKIs

From: "Jingqiang LIN" <[email-masked]>
Date: Mon, 2 Jul 2012 14:13:25 +0800

Dear all,
  We design a scheme called RIKE, to support key escrow in PKIs convenient
and efficiently.
This scheme is compatible with X.509 certificates, and a certificate
extension is needed for this scheme.

The basic idea is as follows.
1. Application Requirement
The key pair for digital signatures shall NOT be escrowed, but the key pair
of for confidentiality usually shall be escrowed.
These two conflicting requirements can exist in one certain entity.

2. Current Solution
An entity owns two certificates and consequently two key pairs.
One is escrowed and used for confidentiality.
The other is not escrowed and used for digital signatures.
The key usage extension is needed to indicate its purposes.

3. Our Solution - RIKE
An entity with these two conflicting requirements, owns only ONE certificate
for digital signatures.
The corresponding key pair is not escrowed.
At the same time, a public key for confidentiality is derived from (the hash
value of) the certificate based on an IBE algorithm.
An IBE private key is inherently escrowed.
Note that, an IBE public key usually is derived from an “identity”,
but in the RIKE solution, an IBE public key is derived from the entity’s
“certificate”.
The entity obtains the corresponding IBE private key from the CA (or other
special component).

4. Benefit
An entity has only ONE certificate, but TWO key pairs are published via the
certificate.
One is escrowed inherently, and the other is not escrowed.
Then, one of these two key pairs can be used for digital signatures, and the
other can be used for confidentiality.
A PKI client queries and validates one certificate from the PKI repository,
but he or she obtains two key pairs.

5. Certificate Extension
The IBE algorithm OID and the public parameters of the IBE algorithm are
embedded as a certificate extension in the user's certificate.
The information is needed to derive the IBE public key of the user.

If this proposal is adopted, I would like to take the drafting task.
If PKIX WG is not interested, I plan to submit it as an individual
submission.

Thanks very much.

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Jingqiang Lin
+8610-82546531
+86-18910039067
Chinese Academy of Sciences
   Institute of Information Engineering
   Data Assurance and Communication Security Center
   State Key Laboratory of Information Security
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