1. RSA Laboratories’ PKCS Series - a Tutorial
Magnus Nyström, RSA Laboratories
October, 1999

2. Agenda Part I: Background Part II: An ASN.1 Primer (if needed)
Some history
Cryptographic background information
Things that needs to be standardized
Part II: An ASN.1 Primer (if needed)
Part III: Review of Active Documents:
PKCS #1
PKCS #5
PKCS #7
PKCS #8
PKCS #9
PKCS #10
PKCS #11
PKCS #12
PKCS #13
PKCS #14
PKCS #15

3. …should make for a full half-day!

4. PKCS “Distinctive” Purpose: Scope: Process:
catalyst for formal and de facto standards
“missing pieces”
Scope:
public-key infrastructure, as well as cryptography
Process:
“informal,” “intervendor”

5. Background
PKCS series created in the early 1990’s to promote public-key cryptography
Initial documents defined
RSA Encryption/Decryption
RSA Signatures/Verification
Diffie-Hellman key exchanges
Password-based encryption
Extended certificates (remember, only X.509v1 available at the time)
Enveloping of messages

6. Background, Continued
RSA Laboratories’ role in the standards-making process
Publish the documents
Solicit opinions and request for changes from developers
Publish revised versions whenever appropriate
Provide implementation guidelines
RSA Laboratories’ retain the sole decision-making authority
Different from “normal” standards-committee work

7. Background, Continued
This gives a quick process - normally less than one year for a new specification
Goal is not to retain ownership of these documents, but to facilitate “early adoption”, e.g.:
PKCS #6 -> X.509 v3
PKCS #7 -> IETF CM
PKCS #15 -> ISO (perhaps)

8. Some Cryptographic Background
We’ll look at
Public-key cryptography
Secret-key cryptography
Message-digest algorithms

9. Public-Key Cryptography
“Invented” by Diffie and Hellman in 1976
Each party has one private key and one public
Applications
Signatures
Key agreements (Key exchanges)
Authentication
Examples:
RSA
Elliptic Curves
Diffie-Hellman

10. Secret-Key Cryptography
Each pair of parties must share a secret key
Applications
Message encryption
Authentication
Signatures
Examples
DES
RSA’s RC2, RC4, RC5 and RC6
IDEA (J. Massey)

11. Message Digests Transform a message of any length to a fixed length
Cryptographic hash functions are used for this purpose:
Collision-resistant
One-way
Examples:
RSA’s MD2, MD4 and MD5
SHA-1, SHA-2

12. The Need for Standardization
Digital Signatures:
Message-Digest algorithms (PKCS #1)
Public-Key algorithms (PKCS #1, PKCS #3, PKCS #13)
Syntax for signed messages (PKCS #7)
Storage of private keys
Syntax for private keys (PKCS #1, PKCS #8)
Syntax for encrypted private keys (PKCS #8)
Methods for deriving secret keys from passwords (PKCS #5)

13. The Need for Standardization, II
Digitally-Enveloped messages
Message syntax (PKCS #7)
Secret-Key algorithms (PKCS #7)
Public-Key algorithms (for wrapping) (PKCS #1)
Digital Certificates
Syntax (PKCS #6; now historic)
Certificate requests (PKCS #10)
Signature algorithms (PKCS #1)

14. The Need for Standardization, III
Key agreement
Message syntax
Key-Agreement algorithms (PKCS #3)
Storage, access and exchange of cryptographic credentials
Exchange, Storage (PKCS #12, PKCS #15)
Access (PKCS #11)
Generation of pseudorandom numbers
Crucial for security; needs good guidelines (PKCS #14)