ISC2 Systems Security Certified Practitioner (SSCP) Practice Question

Encrypting large files directly with RSA is inefficient because asymmetric operations on large integers are slow and each small plaintext block expands to the full modulus size. Switching to a symmetric algorithm such as AES eliminates the heavy public-key computations and keeps ciphertext almost the same size as the plaintext (plus a small tag).

Using AES-256-GCM meets every requirement: it provides 256-bit symmetric strength-well above the ≈112-bit strength of RSA-2048-while GCM adds authenticated-encryption integrity. AWS KMS can generate a random 256-bit data key, perform envelope encryption, and securely store the wrapped key.

Increasing the RSA key to 4096 bits would further slow processing and double ciphertext size. Triple DES is slower than AES, offers only about 112-bit effective strength, and uses 64-bit blocks that are less efficient. AES-128 in ECB would be fast and at 128-bit strength still exceeds RSA-2048's security, but ECB leaks plaintext patterns and lacks integrity protection, violating confidentiality goals. Therefore, AES-256-GCM with a KMS-wrapped data key is the best option.