mod_ssl Chapter 7
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F.A.Q. List

``I know you believe you understand what you think I said, but I am not sure you realize that what you heard is not what I meant.''
Richard Nixon
The positive identification of a network entity such as a server, a client, or a user. In SSL context the server and client Certificate verification process.

Access Control
The restriction of access to network realms. In Apache context usually the restriction of access to certain URLs.

An unambiguous formula or set of rules for solving a problem in a finite number of steps. Algorithms for encryption are usually called Ciphers.

A data record used for authenticating network entities such as a server or a client. A certificate contains X.509 information pieces about its owner (called the subject) and the signing Certificate Authority (called the issuer), plus the owner's public key and the signature made by the CA. Network entities verify these signatures using CA certificates.

Certification Authority (CA)
A trusted third party whose purpose is to sign certificates for network entities it has authenticated using secure means. Other network entities can check the signature to verify that a CA has authenticated the bearer of a certificate.

Certificate Signing Request (CSR)
An unsigned certificate for submission to a Certification Authority, which signs it with the Private Key of their CA Certificate. Once the CSR is signed, it becomes a real certificate.

An algorithm or system for data encryption. Examples are DES, IDEA, RC4, etc.

The result after a Plaintext passed a Cipher.

Configuration Directive
A configuration command that controls one or more aspects of a program's behavior. In Apache context these are all the command names in the first column of the configuration files.

A HTTP command for proxying raw data channels over HTTP. It can be used to encapsulate other protocols, such as the SSL protocol.

Digital Signature
An encrypted text block that validates a certificate or other file. A Certification Authority creates a signature by generating a hash of the Public Key embedded in a Certificate, then encrypting the hash with its own Private Key. Only the CA's public key can decrypt the signature, verifying that the CA has authenticated the network entity that owns the Certificate.

Diminished in cryptographic strength (and security) in order to comply with the United States' Export Administration Regulations (EAR). Export-crippled cryptographic software is limited to a small key size, resulting in Ciphertext which usually can be decrypted by brute force.

Fully-Qualified Domain-Name (FQDN)
The unique name of a network entity, consisting of a hostname and a domain name that can resolve to an IP address. For example, www is a hostname, is a domain name, and is a fully-qualified domain name.

HyperText Transfer Protocol (HTTP)
The HyperText Transport Protocol is the standard transmission protocol used on the World Wide Web.

The HyperText Transport Protocol (Secure), the standard encrypted communication mechanism on the World Wide Web. This is actually just HTTP over SSL.

Message Digest
A hash of a message, which can be used to verify that the contents of the message have not been altered in transit.

The Open Source toolkit for SSL/TLS; see

Pass Phrase
The word or phrase that protects private key files. It prevents unauthorized users from encrypting them. Usually it's just the secret encryption/decryption key used for Ciphers.

The unencrypted text.

Private Key
The secret key in a Public Key Cryptography system, used to decrypt incoming messages and sign outgoing ones.

Public Key
The publically available key in a Public Key Cryptography system, used to encrypt messages bound for its owner and to decrypt signatures made by its owner.

Public Key Cryptography
The study and application of asymmetric encryption systems, which use one key for encryption and another for decryption. A corresponding pair of such keys constitutes a key pair. Also called Asymmetric Crypography.

Secure Sockets Layer (SSL)
A protocol created by Netscape Communications Corporation for general communication authentication and encryption over TCP/IP networks. The most popular usage is HTTPS, i.e. the HyperText Transfer Protocol (HTTP) over SSL.

The context information of an SSL communication.

The original SSL/TLS implementation library developed by Eric A. Young <>; see

Symmetric Cryptography
The study and application of Ciphers that use a single secret key for both encryption and decryption operations.

Transport Layer Security (TLS)
The successor protocol to SSL, created by the Internet Engineering Task Force (IETF) for general communication authentication and encryption over TCP/IP networks. TLS version 1 and is nearly identical with SSL version 3.

Uniform Resource Locator (URL)
The formal identifier to locate various resources on the World Wide Web. The most popular URL scheme is http. SSL uses the scheme https

An authentication certificate scheme recommended by the International Telecommunication Union (ITU-T) which is used for SSL/TLS authentication.

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mod_ssl 2.8, User Manual
The Apache Interface to OpenSSL
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