Encryption

How does it work? Encryption is based on "one way, trap door functions." These are functions that are easy to calculate, but hard to reverse unless you have a "key."

Public key cryptographic system: Users have a public and a private key. If I want you to send me an encrypted document, I send you my public key to encrypt it. You send it to me and only I can decrypt it with my private key.

Escrowed Encryption: government vs commercial key holders

DES: Data Encryption Standard-developed by the NSA and IBM, 1976. It is used in banking and utilized private key encryption. This was controversial since many did not trust the NSA. It is based on a "block" cipher. The same key is used to both encrypt and decrypt, except that the key is used in reverse order. Data is encrypted in 64 bit blocks.

AES: NIST is considering proposals for the Advanced Encryption Standard which is to replace DES. It will encrypt data in 128 bit blocks.

Clipper clip: Key escrow system, used the Skipjack algorithm. Every message would contain a LEAF-Law Enforcement Access Field, which would tell law enforcement how to decrypt a message.

RSA: This is an algorithm patented by Rivest, Shamir, and Adleman. It's used in public key encryption and for digital signatures. RSA is based on the factoring of large, prime numbers. The security is dependent on the size of the numbers being factored.

PGP: "Pretty Good Privacy" This is a method of encrypting email released by Phil Zimmermann in 1991. Some called it "Pretty Good Piracy" since it was based on the RSA algorithm. Zimmermann was the subject of a Federal Investigation for violating export restrictions, but charges were eventually dropped.

Applications of Encryption

Encryption Related Issues

Since encryption has many military uses, it has been classifies as a "munition." Export has been highly restricted. Only weak encryption is legal for export. The SPA Software Publishers of America found that encryption methods not legal for export from the US are readily available world wide.

SAFE: Security and Freedom through Encryption

CALEA: Communications Assistance for Law Enforcement, 1996. This legislation ensures that law enforcement will be able to wiretap digital communications. EFF (Electronic Frontier Foundation) and EPIC (Electronic Privacy Information Center) have voiced objections to CALEA.

Questions:
For more information see: Bruce Schneier, Applied Cryptography. Wiley, 1994.

To learn about PGP at Mason, see: http://www.cs.gmu.edu/~amarchan/cs108/pgp.html

To get started learning about cryptography, see: The CipherSaber Homepage by Arnold G. Reinhold and
John Savard's Homepage (includes history of cryptography).

For Digital Watermarking, see: Steganography and Digital Watermarking by GMU's own Neil Johnson.