Handbook of Information Security: Information Warfare, Social, Legal, and International Issues and Security Foundations, Volume 2

Encryption Basics

Ari Juels, RSA Laboratories

Introduction

Some Basics

A Brief Historical Note

Symmetric-Key Encryption: Introduction

Symmetric-Key Encryption Today

More on the Security of Symmetric-Key Encryption

Encryption and Passwords

Public-Key Cryptography

Diffie–Hellman Key Exchange

The RSA Cryptosystem

More Technical Detail on RSA

How Public-Key Encryption Is Used

Conclusion: Further Reading

Glossary

Cross References

References

INTRODUCTION

Encryption is the procedure of rendering a message into a concealed form so that it is decipherable exclusively by a particular recipient or recipients. The message in its original state is known as a plaintext (or cleartext); in its encrypted form, it is known as a ciphertext. Historically, the aim of encryption has been to enable two parties to exchange messages confidentially, even in the presence of an eavesdropper capable of intercepting most or all of their communications. The use of encryption has been confined chiefly to diplomatic and military circles in the past, but its scope in everyday life has broadened enormously in recent years. Thanks to the rise of the Internet, it is estimated that over half a billion personal computers are equipped today with strong encryption capabilities in their Web browsing software. This includes nearly every new computer sold today.

Active users of the Internet employ encryption on a regular basis. When accepting credit card information or processing other financial transactions, most Web servers ...