Here's a comprehensive summary of the article on 40-bit encryption:
40-bit encryption refers to a symmetric key size of forty bits, or 2^40 possible keys, which offered a very low and now completely broken level of security. This limited key length made it highly vulnerable to brute-force attacks; for instance, the Electronic Frontier Foundation's Deep Crack machine could break a 40-bit key in about two seconds in 1998, and a home computer could do so in weeks by 2004. This weak encryption was widely adopted in software released before 1999, including international versions of web browsers and early Wired Equivalent Privacy (WEP), primarily due to restrictive U.S. export regulations that prohibited the sale of stronger encryption (like 56-bit DES) overseas. Consequently, 40-bit encryption is entirely obsolete and cannot be considered secure. Modern symmetric encryption, such as AES, now universally employs much stronger key lengths of 128, 192, or 256 bits for secure communications.