Exam CAS-004 topic 1 question 239 discussion

Forward secrecy is a feature that ensures that encrypted communications are secure even if the private keys are compromised in the future. Authenticated encryption with associated data (AEAD) is a mode of encryption that provides confidentiality, integrity, and authenticity. GCM (Galois/Counter Mode) is a block cipher mode that provides AEAD encryption, authenticity, and integrity. AES (Advanced Encryption Standard) is a symmetric block cipher algorithm used in GCM mode for providing encryption. ECDSA (Elliptic Curve Digital Signature Algorithm) is a public-key cryptographic algorithm used to provide authentication.

C. GCM Correct because GCM (Galois/Counter Mode) provides authenticated encryption. It supports associated data integrity along with confidentiality. It meets the requirement for authenticated encryption in the cipher suite. D. AES Correct because AES is a strong symmetric encryption algorithm. When used with an AEAD mode like GCM, it provides both confidentiality and data integrity. It is commonly used in TLS cipher suites combined with key exchange mechanisms that offer forward secrecy. H. DH Correct because DH (Diffie-Hellman) can be employed in an ephemeral mode (DHE) to ensure forward secrecy. It provides a key exchange mechanism that allows the establishment of secure session keys. It complements the use of strong encryption algorithms like AES/GCM in TLS.

DH on its own does not inherently have forward secrecy; to achieve forward secrecy, a system would need to utilize a key exchange mechanism like Diffie-Hellman, specifically in its "ephemeral" mode (DHE or ECDHE), which generates unique session keys for each connection, preventing past communication from being compromised even if a long-term private key is breached

ECDSA (Elliptic Curve Digital Signature Algorithm): Used for digital signatures, not for encryption or key exchange.

To meet the requirements of forward secrecy and authenticated encryption with associated data, the following algorithms should be combined: C. GCM — Provides authenticated encryption with associated data (AEAD), ensuring both confidentiality and integrity. D. AES — A strong block cipher that, when used with GCM, provides the encryption layer. H. DH — Provides ephemeral key exchange for forward secrecy (use ECDHE for elliptic curve variant). And not G. ECDSA (Elliptic Curve Digital Signature Algorithm) Explanation: ECDSA is a public key signature algorithm, used for digital signatures rather than key exchange. While it can be used for authentication and integrity checking, it does not directly provide forward secrecy. However, ECDSA can be used as part of a cipher suite when paired with an appropriate key exchange mechanism (like ECDHE). It is not a key exchange algorithm on its own.

ChatGPT goes with C, D and H.

While ECDSA (Elliptic Curve Digital Signature Algorithm) is important for digital signatures and ensuring data integrity and authenticity, it does not contribute to forward secrecy. Therefore, for the specific requirement of forward secrecy and AEAD, DH (or its elliptic curve variant ECDHE) is the appropriate choice.

ECDSA (Elliptic Curve Digital Signature Algorithm): Provides efficient and secure digital signatures, which are crucial for server authentication. GCM (Galois/Counter Mode): Provides authenticated encryption with associated data (AEAD). AES (Advanced Encryption Standard): A widely used and strong encryption standard.

Sorry, ECDSA does not has DH.

CDG, Diffie-Hellman is in ECDSA.

To achieve forward secrecy and authenticated encryption with associated data (AEAD), the security engineer should choose the following algorithms: C. GCM (Galois/Counter Mode): GCM provides authenticated encryption with associated data (AEAD) and is widely used for its efficiency and security. D. AES (Advanced Encryption Standard): AES is a symmetric encryption algorithm commonly used in conjunction with GCM for AEAD. G. ECDSA (Elliptic Curve Digital Signature Algorithm): ECDSA is commonly used for digital signatures in TLS, providing authentication and integrity.

Pretty confident on this one. You would not use ECDSA (Elliptic Curve Digital Signature Algorithm) in this situation. That is for digital signatures and not for sending data. DH when using its ephemeral form (EDH or DHE) would provide forward secrecy. RSA would not be used in conjunction with AES, it would be either or.

To achieve forward secrecy and authenticated encryption with associated data (AEAD), you should use modern and secure cipher suites. Here are three algorithms that, when combined into a cipher suite, meet these requirements: C. GCM (Galois/Counter Mode): GCM provides both authenticated encryption and the ability to achieve forward secrecy when used with appropriate key exchange mechanisms like ECDHE or DHE. D. AES (Advanced Encryption Standard): AES is a symmetric encryption algorithm commonly used with AEAD cipher suites. E. RSA (Rivest–Shamir–Adleman): While RSA is not typically used for forward secrecy, it can be used for authentication in conjunction with other algorithms that provide forward secrecy.

The correct answers are C, D, and H.

The three algorithms that, when combined into a cipher suite, provide forward secrecy and authenticated encryption with associated data are: C. GCM (Galois/Counter Mode) D. AES (Advanced Encryption Standard) H. DH (Diffie-Hellman) ECDSA is an algorithm used for digital signatures and is not directly related to encryption, so it cannot be used for authenticated encryption with associated data. It is typically used in TLS for certificate signing and verification. Therefore, ECDSA cannot be used to meet the requirements of forward secrecy and authenticated encryption with associated data in the given scenario.

Answer is C,D,G