1. Allowed uses of Public Keys Jim Schaad Soaring Hawk Consulting

2. Usage Question RSA Key is a data structure independent of how it is used –DH and DSA OAEP – PSS – PKCS v1.5 are all different usage schemes for that data Should usage restrictions be specified? How should usage be restricted?

3. Possible Answers Never restrict usage –Use rsaEncryption as public key OID Tie to the public key structure –Would do a single usage restriction –Use schema OID as public key OID Use a certificate extension –Allows for multiple usages –Parallels Key Usage Extension –Schema OID restricts key usage

4. OAEP/PSS Complications RSA-OAEP and RSA-PSS specify additional cryptographic parameters (i.e. Mask Generation Function) RSA-OAEP and RSA-PSS specify additional non-cryptographic parameters (i.e. saltLength)

5. Complications (2) Need to specify which are significant –Currently saltLength is specified as a default value Can owner specify multiple items –Can say MFG1 and not MFG1 or MFG2 Can owner make no specification –Requires use of OPTIONAL rather than default

6. Solutions Do nothing Change DEFAULT to OPTIONAL Use separate structures for signature/encryption and public key Create extension to specific this information

7. Solutions (2) Nothing –Requires text to state which items are significant for checking –Allows only a single item to be specified DEFAULT -> OPTIONAL –Those items specified MUST match –Allows only a single item to be specified

8. Solutions (3) Different structure in Public Key field –Allows each OID to specify what they want –Requires different OIDs to be specified for public key vs usage Certificate Extension –Allows for more global specifications Bulk algorithms, hash algorithms –Separates usage information from key data

9. Solutions (4) Nothing Change DEFAULT to OPTIONAL Use separate structures for signature/encryption and public key Create extension to specific this information DISCUSSION