Maria works as a Network Security Officer for Gentech Inc. She wants to encrypt her network traffic. The specific requirement for the encryption algorithm is that it must be a symmetric key block ciph

DES (Data Encryption Standard) is a symmetric key block cipher that operates on 64-bit blocks using a 56-bit key across 16 rounds of a Feistel network, directly satisfying the requirement for a symmetric key block cipher. It was standardized by NIST (then NBS) in 1977 as the definitive example of this cipher category, making it the foundational reference answer for this concept on certification exams.

AES is also technically a symmetric key block cipher - this answer may reflect a poorly scoped question, but DES is the expected answer as the historically foundational symmetric block cipher standard.

PGP (Pretty Good Privacy) is not a cipher but a hybrid encryption framework that combines asymmetric key exchange with symmetric encryption for key distribution, meaning it is not itself a symmetric key block cipher.

IDEA (International Data Encryption Algorithm) is also technically a symmetric key block cipher, but it was a proprietary algorithm with historical patent licensing restrictions that limited its standardized adoption compared to DES.