Glossary of Terms
The process of reliably determining the identity of a communicating party. Identity can be proven by something you know (such as a password), something you have (such as a private key or token), or something intrinsic about you (such as a fingerprint).
A cipher is an encryption algorithm. The cipher you select determines which mathematical algorithm is used to obscure the data being sent after a successful Secure Shell connection has been established.
The assurance that data has not been changed from its original source. Methods to preserve data integrity are designed to ensure that data has not been accidentally or maliciously modified, altered or destroyed.
Used to confirm the authenticity and integrity of a transmitted message. Typically, the sender holds the private key of a public/private key pair and the recipient holds the public key. To create the signature, the sender computes a hash from the message, and then encrypts this value with its private key. The recipient decrypts the signature using the sender's public key, and independently computes the hash of the received message. If the decrypted and calculated values match, the recipient trusts that the sender holds the private key, and that the message has not been altered in transit.
Encryption is the process of scrambling data by use of a secret code or cipher so it is unreadable except by authorized users. Encrypted data is far more secure than unencrypted data.
GSSAPI (Generic Security Services Application Program Interface)
An application programming interface that provides programs with access to security services.
Also called a message digest, a hash or hash value is a fixed-length number generated from variable-length digital data. The hash is substantially smaller than the original data, and is generated by a formula in such a way that it is statistically unlikely that some other text will produce the same hash value.
Kerberos is a protocol that uses a trusted third party to enable secure communications over a TCP/IP network. The protocol uses encrypted tickets rather than plaintext passwords for secure network authentication.
MAC (Message Authentication Code)
Used to verify that data is not changed in transit, a MAC is a hash created using an arbitrary-length packet of data and a shared secret key. The sending and receiving party compute the MAC independently for each packet of transferred data using the shared key and an agreed-upon algorithm. If the message has changed in transit, the hash values are different and the packet is rejected.
A passphrase is similar to a password, except it can be a phrase with a series of words, punctuation, numbers, white space, or any string of characters. Passphrases improve security by limiting access to secure objects, such as private keys and/or a key agent.
A way to redirect unsecured traffic through a secure SSH tunnel. Two types of port forwarding are available: local and remote. Local (also called outgoing) port forwarding sends outgoing data sent from a specified local port through the secure channel to a specified remote port. You can configure a client application to exchange data securely with a server by configuring the client to connect to the redirected port instead of directly to the computer running the associated server. Remote (also called incoming) port forwarding sends incoming data from a specified remote port through the secure channel to a specified local port.
public key/private key
Public keys and private keys are pairs of cryptographic keys that are used to encrypt or decrypt data. Data encrypted with the public key can only be decrypted with the private key; and data encrypted with the private key can only be decrypted with the public key.
Often abbreviated as regex, a regular expression is a string of characters that describes one or more matching strings. Within a regular expression, some characters have a predefined meaning that determines what qualifies as a match. For example, the regular expression "t.*t" matches any word that starts and ends in the letter t, while the regular expression "text" matches only itself.
A protocol for securely logging onto a remote computer and executing commands. It provides a secure alternative to Telnet, FTP, rlogin, or rsh. Secure Shell connections require both server and user authentication, and all communications pass between hosts over an encrypted communication channel. You can also use Secure Shell connections to forward X11 sessions or specified TCP/IP ports through the secure tunnel.
The combination of a host name (IP address or DNS name) and a port number. This creates a unique identifier that a client application uses as an end point of communications.