40-bit Encryption - Obsolescence

Obsolescence

All 40-bit and 56-bit encryption algorithms are obsolete because they are vulnerable to brute force attacks, and therefore cannot be regarded as secure. As a result, virtually all web browsers now use 128-bit keys, which are considered strong. Some web servers will not communicate with a client unless it has a 128-bit encryption capability installed on it.

Public/private key pairs used in asymmetric encryption (public key cryptography) must be much longer than 128 bits for security; see key size for more details.

As a general rule, modern symmetric encryption algorithms such as AES use key lengths of 128, 192 and 256 bits.