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The GNU Privacy Handbook
Copyright © 1999 by The Free Software Foundation
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in thesection entitled "GNU Free Documentation License".
Please direct questions, bug reports, or suggestions concerning this manual to the maintainer, Mike Ashley (<jashley@acm.org>). When referring to the manual please specify which version of the manual you have by using this version string: $Name: v1_1 $.
Contributors to this manual include Matthew Copeland, Joergen Grahn, and David A. Wheeler. JHoracio MG has translated the manual to Spanish.

Table of Contents
1. Getting Started
Generating a new keypair
Generating a revocation certificate
Exchanging keys
Exporting a public key
Importing a public key
Encrypting and decrypting documents
Making and verifying signatures
Clearsigned documents
Detached signatures
2. Concepts
Symmetric ciphers
Public-key ciphersHybrid ciphers
Digital signatures
3. Key Management
Managing your own keypair
Key integrity
Adding and deleting key components
Revoking key components
Updating a key's expiration time
Validating other keys on your public keyring
Trust in a key's owner
Using trust to validate keys
Distributing keys
4. Daily use of GnuPG
Defining your security needs
Choosing a key sizeProtecting your private key
Selecting expiration dates and using subkeys
Managing your web of trust
Building your web of trust
Using GnuPG legally
5. Topics
Writing user interfaces
A. GNU Free Documentation License
0. PREAMBLE
1. APPLICABILITY AND DEFINITIONS
2. VERBATIM COPYING
3. COPYING IN QUANTITY
4. MODIFICATIONS
5. COMBINING DOCUMENTS
6. COLLECTIONS OF DOCUMENTS
7.AGGREGATION WITH INDEPENDENT WORKS
8. TRANSLATION
9. TERMINATION
10. FUTURE REVISIONS OF THIS LICENSE
How to use this License for your documents
List of Figures
3-1. A hypothetical web of trust

Chapter 1. Getting Started
GnuPG is a tool for secure communication. This chapter is a quick-start guide that covers the core functionality of GnuPG. This includes keypair creation, exchanging andverifying keys, encrypting and decrypting documents, and authenticating documents with digital signatures. It does not explain in detail the concepts behind public-key cryptography, encryption, and digital signatures. This is covered in Chapter 2. It also does not explain how to use GnuPG wisely. This is covered in Chapters 3 and 4.
GnuPG uses public-key cryptography so that users may communicatesecurely. In a public-key system, each user has a pair of keys consisting of a private key and a public key. A user's private key is kept secret; it need never be revealed. The public key may be given to anyone with whom the user wants to communicate. GnuPG uses a somewhat more sophisticated scheme in which a user has a primary keypair and then zero or more additional subordinate keypairs. Theprimary and subordinate keypairs are bundled to facilitate key management and the bundle can often be considered simply as one keypair.

Generating a new keypair
The command-line option --gen-key is used to create a new primary keypair.
alice% gpg --gen-key
gpg (GnuPG) 0.9.4; Copyright (C) 1999 Free Software Foundation, Inc.
This program comeswith ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it
under certain conditions. See the file COPYING for details.

Please select what kind of key you want:
(1) DSA and ElGamal (default)
(2) DSA (sign only)
(4) ElGamal (sign and...