The FREE Cybersecurity Glossary by Thor Pedersen!

Transport Layer Security (TLS): A cryptographic protocol designed to provide secure communication across a network. The protocol uses asymmetric cryptography for authentication, symmetric encryption for privacy, and message authentication codes for message integrity. It's extensively used in web browsing, email, instant messaging, and voice-over-IP (VoIP), among other applications.

Transport Mode (in IPSec): In IPSec, transport mode encrypts only the payload of the IP packet, not the IP header itself, which is left intact. It's mainly used for end-to-end communications, such as encrypting data for VPN connections between two hosts.

Transposition and Permutation: In cryptography, transposition refers to rearranging the characters in a message, while permutation involves rearranging bits, bytes, or other parts of data according to a specific rule or system. Both techniques are used to obscure the content for security purposes.

Trapdoor function: A function that is easy to compute in one direction but believed to be difficult to compute in the opposite direction without special information, called a 'trapdoor'. These functions are essential in the construction of encryption algorithms, particularly public-key cryptosystems.

Tree Topology: A type of network topology structured in a hierarchy, with a single 'root' node (typically a switch or a hub) that connects multiple sets of 'branches' (sub-networks), resembling a tree structure. It allows for the expansion of an existing network and is instrumental in organizing the networks in a manageable fashion.

Trivial File Transfer Protocol (TFTP): A simplified version of the FTP protocol that is used to transfer files over networks. Unlike FTP, it doesn't require user authentication and operates on UDP, making it faster but less secure. It is commonly used in devices like routers or IP phones for firmware or configuration uploads.