Mary Jean Harrold 1 CS 4001

Class 9

Questions about term paper—list of possible topics available on line—proposal due 9/27

Communications assignment—discuss Finish communications discussion

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Intercepting Communications (cont’d)

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Outline

Overview of the Controversies

Intercepting Communications

Cryptography and Its Uses

Encryption Policy: Access to Software, Keys,

and Plaintext

Fundamental Issues

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Q1: Are there other ways to hide a message in plain sight?

Cryptography and Its Uses (1)

Cryptography Definition:

Hiding data in plain sight.

Terms: Plaintext: Original, readable message or data. Cyphertext: Modified, unreadable message or data. Encryption: The act of converting plaintext into cyphertext. Decryption: The act of reverting cyphertext back to readable,

plaintext.

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Cryptography and Its Uses (2)

Public Key Cryptography How it works:

User creates a mathematically-related key pair (public and private keys).

Public keys are shared publicly; private keys are kept secret. Public keys are used to encrypt message or data. Private keys are used to decrypt message or data.

Benefits: No secret keys need be shared or transmitted. Very secure.

Q2: How does key-size affect the ‘strength’ of encryption?

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Q3: Why are strong encryption tools needed by human-rights activists?

Cryptography and Its Uses (3)

Encryption Used by:

Military personnel. Financial institutions. Human-rights activists. Government agencies. Anyone wanting to keep messages or data private.

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Cryptography and Its Uses (4)

Steganography Definition:

Hiding data so that its existence is not known.

Examples: Digital watermarks. Hiding text in image files.

Used by: Military, Publishers, Anyone wishing to hide messages or data.

Q4: How might steganography be incorporated into textbooks? Why?

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Encryption Policy: Access to Software, Keys, and Plaintext

Secrecy and Export Controls Control of Secrecy

The NSA designs unbreakable codes for the U.S. government. The NSA attempts to break codes used by other governments. In the past, the NSA also controlled the funding for and publishing

of cryptographic research.

Control of Exportation Early U.S. policy prevented the exportation of strong encryption. Meanwhile, foreign production and use of strong encryption

negatively impacted U.S. competition in the world market. Cryptographic researchers, privacy advocates, and others

successfully challenged exportation restrictions.Q5: Why did the U.S. government insist on controlling export of strong crypto?

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Fundamental Issues (1)

Role of Secrecy U.S. Policy Keeps Secret:

Cryptographic research. Wiretap ease or difficulty. Encryption algorithms. Software (e.g. Carnivore). Global endeavors (e.g. Echelon).

Problems: Secret algorithms cannot be tested by experts. ‘Backdoors’ might exist. NSA-influenced wiretap and encryption exportation bills

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Q7: Today, do coders or decoders have the upper hand?

Fundamental Issues (2)

The Ever-changing Status Quo Past:

Simple codes and cyphers.

Present: 512-bit RSA encryption. AES (Advanced Encryption Standard).

Future: Quantum computing. Quantum cryptography.

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Trust in Government Appropriate or Abusive?

Wiretapping by FBI and local police. Wiretapping by NSA. Strong encryption restrictions. Roving wiretaps. Cell-phone tracking (and E-911). Development of a nationwide standard for surveillance. Immediate decryption technology built in to the Internet.

Fundamental Issues (3)