Cryptography and Network Security (4th Edition)

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15.1 Pretty Good Privacy

Notation

Operational Description

Cryptographic Keys and Key Rings

Public-Key Management

15.2 S/MIME

RFC 822

Multipurpose Internet Mail Extensions

S/MIME Functionality

S/MIME Messages

S/MIME Certificate Processing

Enhanced Security Services

15.3 Key Terms, Review Questions, and Problems

Key Terms

Review Questions

Problems

Appendix 15A Data Compression Using ZIP

Compression Algorithm

Decompression Algorithm

Appendix 15B Radix-64 Conversion

Appendix 15C PGP Random Number Generation

True Random Numbers

Pseudorandom Numbers

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Despite the refusal of VADM Poindexter and LtCol North to appear, the Board's access to other sources of information filled much of this gap. The FBI provided documents taken from the files of the National Security Advisor and relevant NSC staff members, including messages from the PROF system between VADM Poindexter and LtCol North. The PROF messages were conversations by computer, written at the time events occurred and presumed by the writers to be protected from disclosure. In this sense, they provide a first-hand, contemporaneous account of events.

The Tower Commission Report to President Reagan on the Iran-Contra Affair, 1987

Bless the man who made it, And pray that he ain't dead. He could've made a million If he'd sold it to the feds, But he was hot for freedom; He gave it out for free. Now every common citizen's got PGP.

From the song "P.G.P."by Leslie Fish

Key Points

  • PGP is an open-source freely available software package for e-mail security. It provides authentication through the use of digital signature; confidentiality through the use of symmetric block encryption; compression using the ZIP algorithm; e-mail compatibility using the radix-64 encoding scheme; and segmentation and reassembly to accommodate long e-mails.

  • PGP incorporates tools for developing a public-key trust model and public-key certificate management.

  • S/MIME is an Internet standard approach to e-mail security that incorporates the same functionality as PGP.

In virtually all distributed environments, electronic mail is the most heavily used network-based application. It is also the only distributed application that is widely used across all architectures and vendor platforms. Users expect to be able to, and do, send mail to others who are connected directly or indirectly to the Internet, regardless of host operating system or communications suite.

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With the explosively growing reliance on electronic mail for every conceivable purpose, there grows a demand for authentication and confidentiality services. Two schemes stand out as approaches that enjoy widespread use: Pretty Good Privacy (PGP) and S/MIME. Both are examined in this chapter.

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