Specifications

Glossary
GL-4
Cisco Security Appliance Command Line Configuration Guide
OL-6721-01
CTIQBE
Computer Telephony Interface Quick Buffer Encoding. A protocol used in IP telephony between the
Cisco CallManager and CTI TAPI and JTAPI applications. CTIQBE is used by the TAPI/JTAPI
protocol inspection module and supports NAT, PAT, and bi-directional NAT. This enables Cisco IP
SoftPhone and other Cisco TAPI/JTAPI applications to communicate with Cisco CallManager for call
setup and voice traffic across the security appliance.
cut-through proxy
Enables the security appliance to provide faster traffic flow after user authentication. The cut-through
proxy challenges a user initially at the application layer. After the security appliance authenticates the
user, it shifts the session flow and all traffic flows directly and quickly between the source and
destination while maintaining session state information.
D
data confidentiality
Describes any method that manipulates data so that no attacker can read it. This is commonly achieved
by data encryption and keys that are only available to the parties involved in the communication.
data integrity
Describes mechanisms that, through the use of encryption based on secret key or public key
algorithms, allow the recipient of a piece of protected data to verify that the data has not been modified
in transit.
data origin
authentication
A security service where the receiver can verify that protected data could have originated only from
the sender. This service requires a data integrity service plus a key distribution mechanism, where a
secret key is shared only between the sender and receiver.
decryption
Application of a specific algorithm or cipher to encrypted data so as to render the data comprehensible
to those who are authorized to see the information. See also encryption.
DES
Data encryption standard. DES was published in 1977 by the National Bureau of Standards and is a
secret key encryption scheme based on the Lucifer algorithm from IBM. Cisco uses DES in classic
crypto (40-bit and 56-bit key lengths), IPSec crypto (56-bit key), and 3DES (triple DES), which
performs encryption three times using a 56-bit key. 3DES is more secure than DES but requires more
processing for encryption and decryption. See also AES, ESP.
DHCP
Dynamic Host Configuration Protocol. Provides a mechanism for allocating IP addresses to hosts
dynamically, so that addresses can be reused when hosts no longer need them and so that mobile
computers, such as laptops, receive an IP address applicable to the LAN to which it is connected.
Diffie-Hellman
A public key cryptography protocol that allows two parties to establish a shared secret over insecure
communications channels. Diffie-Hellman is used within IKE to establish session keys.
Diffie-Hellman is a component of Oakley key exchange.
Diffie-Hellman
Group 1, Group 2,
Group 5, Group 7
Diffie-Hellman refers to a type of public key cryptography using asymmetric encryption based on
large prime numbers to establish both Phase 1 and Phase 2 SAs. Group 1 provides a smaller prime
number than Group 2 but may be the only version supported by some IPSec peers. Diffe-Hellman
Group 5 uses a 1536-bit prime number, is the most secure, and is recommended for use with AES.
Group 7 has an elliptical curve field size of 163 bits and is for use with the Movian VPN client, but
works with any peer that supports Group 7 (ECC). See also VPN and encryption.
digital certificate
See certificate.
DMZ
See interface.