Backdoors are usually inserted into a program or algorithm before it is distributed widely. They are often hidden in part of the design of the program or algorithm. In cryptography specifically, a backdoor would allow an intruder to access the encrypted information without having the correct credentials.
A backdoor is a built-in way of circumventing that type of encryption. It essentially allows a manufacturer to access all the data on any device it creates. And it's nothing new—this reaches all the way back to the abandoned “Clipper chip” in the early '90s. Many things can serve as a backdoor.
A backdoor refers to any method by which authorized and unauthorized users are able to get around normal security measures and gain high level user access (aka root access) on a computer system, network or software application.
A backdoor Trojan gives malicious users remote control over the infected computer. They enable the author to do anything they wish on the infected computer – including sending, receiving, launching, and deleting files, displaying data, and rebooting the computer.
Backdoors can look like normal php code or obfuscated (intentionally obscured to make code ambiguous) and hidden. ... Backdoor access allows an attacker to place any malicious code on the site. Backdoors are often found in conjunction with other malware.
Key escrow is a method of storing important cryptographic keys. Each key stored in an escrow system is tied to the original user and subsequently encrypted for security purposes. Much like a valet or coat check, each key is stored in relation to the user that leverages it, and then returned once queried.