What is the recommended minimum effective key strength for new cryptographic implementations?

• A. 112 bits
• B. 256 bits
• C. 128 bits
• D. 64 bits

Answer: (C)

The level of security hinges on how hard it is to brute-force the key. For new cryptographic implementations, the minimum acceptable strength is 128 bits. With 128-bit keys, there are 2^128 possible keys, which current and near-future computing cannot realistically exhaust, so the cipher remains secure for the foreseeable future. A 64-bit key is far too small and can be cracked quickly with today’s hardware, so it’s inappropriate for new deployments. An effective strength of 112 bits is an improvement over older schemes but is not considered sufficient as a baseline for new systems because it could become vulnerable sooner than 128-bit schemes. While using 256-bit keys is perfectly valid and even stronger, it exceeds the minimum requirement.