1. Jim Schaad Soaring Hawk Security
RFC 2511 BIS (CRMF)
Jim Schaad
Soaring Hawk Security

2. Proof of Possession (POP)
Provide evidence that the following two conditions are met
I have use of the private key
My identity is <your name here>
Owner of key can always produce a false POP for somebody else

3. POP - Methods Document defines 6 different methods for POP
Signature Based
Surrender of private key
Direct (Challenge Response)
Indirect (Decrypt Certificate)
Key Agreement HMAC
RA Asserts POP is completed

4. POP - Sign Sign Satisfies the POP requirement Public Key
Identity Statement
Satisfies the POP requirement

5. POP – Surrender Private Key
Encrypt private key for the CA/RA
Proves key possession only.
Allows for theft of POP proof.
Sufficient to do?
ECA(private key, identity statement)
Encrypted structure currently not specified.
CMS? Other? Content?

6. POP – Direct/Indirect Receive EEE(value) Decrypt and return value
Shows use of key
Does not show identity
Does it need to be fixed – if so how?

7. POP – DH-HMAC Produce a shared secret with CA/RA
HMAC the request with derived key
Send result with enrollment message
Proves use of private key
Proves identity sometimes
Need to ensure identity is in the hashed value at all times

8. Blocking Issues POP issues as previously noted
DH-MAC needs to be extended for other key – provide algorithm and value
Protocol Encryption Key Control
Specifies key, but not any algorithms

9. Blocking Issues Reg Token and Authenticator control
Can’t do binary in UTF8 string
Type has changed but not OID since RFC 2511
Reg Token algorithm undefined if computed
Need better distinguishing text

10. Blocking Issues Archival Key Gen parameter structure not defined
Key Gen parameter structure not encrypted
Encryption key not specified
CA? RA? User’s?
Discovery of encryption algorithms to use

11. Blocking Issues RegInfo Control overloads the use of ‘%’
Name?Value%[Name?Value%]*
%xx if % and ? Not be used as delimiters

12. Questions