Hash Transition Updates

1
Hash Transition Updates

• Jim Schaad
• Soaring Hawk Consulting

2
ESSCertID

• Currently
• SHA-1 HASH of entire certificate
• Optional issuer and serial number of cert
• Proposed Update
• HASH of entire certificate
• Hash identifier of entire certificate
• Optional issuer and serial number of cert

3
Parallel Signing Indicator

• Problem Statement
• Alice signs using both SHA-1 and SHA-256
• Mallory removes the SHA-256 signature and
  successfully attacks SHA-1
• Bob can do SHA-256, but does not know that the
  parallel signature has been removed

4
Solution

• New signed attribute signaling that multiple
  signatures were applied
• Must be computable BEFORE any signatures are
  applied
• Must contain enough information to identify back
  to signatures in some fashion

5
Possible Data

• Body Digest algorithm
• Signature algorithm
• Identification of public key used for signature

6
Questions