An IoT developer needs to ensure that user passwords for a smartphone app are stored securely. Which of the following methods should the developer…

While the industry best practice for password storage is using a salted, slow hashing algorithm (like Argon2 or bcrypt), this is not an available option. Among the choices provided, Advanced Encryption Standard with a 256-bit key (AES-256) is a strong, widely-adopted, and NIST-standardized symmetric encryption algorithm. It offers a high level of confidentiality for the stored data. Although encryption is reversible—a significant drawback for password storage—its cryptographic strength is vastly superior to using a broken hashing algorithm like MD5 or storing passwords in plaintext. Therefore, it is the most secure method presented in the question.

B. Twofish is a secure algorithm, but AES is the current NIST standard and is more widely implemented. AES-256 also offers a larger key size in this comparison.

C. Message Digest 5 (MD5) is a cryptographically broken hashing algorithm. It is vulnerable to collision and rainbow table attacks, making it completely unsuitable for password security.

D. Storing passwords in read-only memory is not a security method. It provides no cryptographic protection, leaving the passwords in plaintext and vulnerable to being read if compromised.

1. National Institute of Standards and Technology (NIST). (2001). FIPS PUB 197: Advanced Encryption Standard (AES). This publication specifies AES as the federal information processing standard for encrypting electronic data

establishing it as a trusted and robust encryption algorithm. (Available at: https://doi.org/10.6028/NIST.FIPS.197)

2. National Institute of Standards and Technology (NIST). (2017). Special Publication 800-63B: Digital Identity Guidelines. Section 5.1.1.2

"Memorized Secret Verifiers

" mandates storing passwords as hashes from approved one-way key derivation functions (KDFs) and explicitly states that encryption is not a substitute for this process. This highlights why option A is suboptimal but still better than the insecure alternatives.

3. Turner

S.

& Chen

L. (2011). RFC 6151: Updated Security Considerations for the MD5 Message-Digest and the HMAC-MD5 Algorithms. This document details the known collision and preimage attack vulnerabilities in MD5

concluding it is "no longer acceptable for applications that require collision resistance" and should be considered "cryptographically broken." This directly invalidates option C.

4. Pfleeger

C. P.

Pfleeger

S. L.

& Margulies

J. (2015). Security in Computing (5th ed.). Pearson Education. Chapter 12

"Cryptography in Practice

" discusses the appropriate use of cryptographic primitives. It explains that strong

standardized algorithms like AES are suitable for confidentiality

while hashing is used for integrity and password verification

noting the insecurity of older algorithms like MD5.