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Chapter 7: The OpenSSL Library
Overview
URL: | http://www.openssl.org |
|---|---|
Primary authors: | Various;originally Eric Young and Tim Hudson |
Component type: | C language library, cryptography toolkit including SSL and TLS |
License: | OpenSSL, SSLeay |
Version profiled: | 0.9.7 |
Dependencies: | None |
The OpenSSL Project is a collaborative effort to develop a robust, commercial-grade, fully featured, and Open-Source toolkit implementing the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols as well as a full-strength, general-purpose cryptography (crypto) library. A worldwide community of volunteers that use the Internet to communicate, plan, and develop the OpenSSL toolkit and its related documentation manage the project. OpenSSL's functionality breaks down into two libraries: the SSL/TLS library (libssl.a) and the crypto library (libcrypto.a).Developers most often use the SSL/TLS library, implementing versions 2 and 3 of SSL and version 1 of TLS, to build secure Web transactions via the https protocol. OpenSSL provides a wide range of functionality, including the following:
SSL/TLS protocols
Symmetric cryptographic operations (ciphers, message digests)
Asymmetric cryptographic operations (digital signatures, enveloping)
Public Key Infrastructure (PKI), including OCSP, rich X509 certificate support, certificate verification, certificate requests, and CRLs
Due to the overwhelming size of scope of the SSL/TLS library (more than 200 exported functions), this chapter only focuses on the EVP interface of the crypto library. The crypto library is itself large and includes support for ASN.l, PRNG, big numbers, elliptical curves, and more—none of which we will cover in depth here.The crypto library is extremely useful for building cryptography into applications, and mainstay tools such as ssh, sshd, and isakmpd use it. It offers a wide array of cryptographic functionality in the following key areas:
Symmetric ciphers via the EVP_Cipher () interface
Asymmetric ciphers via the EVP_Seal () and EVP_Open () interfaces
Authentication and hashing via the EVP_Digest() interface
Digital signatures via the EVP_Sign () and EVP_Verify () interfaces
Table 7.1 summarizes the supported algorithms that the crypto library supports.
SYMMETRIC CIPHERS | ASYMMETRIC CIPHERS | MESSAGE DIGESTS |
|---|---|---|
Blowfish | DSA | HMAC |
CAST | DH | MD2 |
DES | RSA | MD4 |
IDEA | MD5 | |
RC2 | MPC2 | |
RC4 | RIPEMD | |
RC5 | SHA | |
SHA1 | ||
