ISC CISSP Dumps Questions Answers

Compressing the data before encryption is a technique that can be used to make an encryption scheme more resistant to a known plaintext attack. A known plaintext attack is a type of cryptanalysis where the attacker has access to some pairs of plaintext and ciphertext encrypted with the same key, and tries to recover the key or decrypt other ciphertexts. A known plaintext attack can exploit the statistical properties or patterns of the plaintext or the ciphertext to reduce the search space or guess the key. Compressing the data before encryption can reduce the redundancy and increase the entropy of the plaintext, making it harder for the attacker to find any correlations or similarities between the plaintext and the ciphertext. Compressing the data before encryption can also reduce the size of the plaintext, making it more difficult for the attacker to obtain enough plaintext-ciphertext pairs for a successful attack.

The other options are not techniques that can be used to make an encryption scheme more resistant to a known plaintext attack, but rather techniques that can introduce other security issues or inefficiencies. Hashing the data before encryption is not a useful technique, as hashing is a one-way function that cannot be reversed, and the encrypted hash cannot be decrypted to recover the original data. Hashing the data after encryption is also not a useful technique, as hashing does not add any security to the encryption, and the hash can be easily computed by anyone who has access to the ciphertext. Compressing the data after encryption is not a recommended technique, as compression algorithms usually work better on uncompressed data, and compressing the ciphertext can introduce errors or vulnerabilities that can compromise the encryption.

The use of private and public encryption keys is fundamental in the implementation of Secure Sockets Layer (SSL). SSL is a protocol that provides secure communication over the Internet by using public key cryptography and digital certificates. SSL works as follows:

• The client initiates a connection to the server and requests its digital certificate, which contains its public key and identity information.
• The server sends its digital certificate to the client, and optionally requests the client’s digital certificate as well.
• The client verifies the server’s digital certificate with a trusted third party, such as a certificate authority (CA), and optionally sends its own digital certificate to the server.
• The server verifies the client’s digital certificate with a trusted third party, if applicable.
• The client and the server use the Diffie-Hellman algorithm to generate a shared secret key, which is used to encrypt and decrypt the data exchanged between them.
• The client and the server use the shared secret key and a symmetric encryption algorithm, such as Advanced Encryption Standard (AES), to establish a secure session and communicate confidentially and reliably.

The use of private and public encryption keys is fundamental in the implementation of SSL because it enables the authentication of the parties, the establishment of the shared secret key, and the protection of the data from eavesdropping, tampering, and replay attacks.

The other options are not protocols or algorithms that use private and public encryption keys in their implementation. Diffie-Hellman algorithm is a method for generating a shared secret key between two parties, but it does not use private and public encryption keys, but rather public and private parameters. Advanced Encryption Standard (AES) is a symmetric encryption algorithm that uses the same key for encryption and decryption, but it does not use private and public encryption keys, but rather a single secret key. Message Digest 5 (MD5) is a hash function that produces a fixed-length output from a variable-length input, but it does not use private and public encryption keys, but rather a one-way mathematical function.

The second phase of Public Key Infrastructure (PKI) key/certificate life-cycle management is the initialization phase. PKI is a system that uses public key cryptography and digital certificates to provide authentication, confidentiality, integrity, and non-repudiation for electronic transactions. PKI key/certificate life-cycle management is the process of managing the creation, distribution, usage, storage, revocation, and expiration of keys and certificates in a PKI system. The key/certificate life-cycle management consists of six phases: pre-certification, initialization, certification, operational, suspension, and termination. The initialization phase is the second phase, where the key pair and the certificate request are generated by the end entity or the registration authority (RA). The initialization phase involves the following steps:

• The end entity or the RA generates a key pair, consisting of a public key and a private key, using a secure and random method.
• The end entity or the RA creates a certificate request, which contains the public key and other identity information of the end entity, such as the name, email, organization, etc.
• The end entity or the RA submits the certificate request to the certification authority (CA), which is the trusted entity that issues and signs the certificates in the PKI system.
• The end entity or the RA securely stores the private key and protects it from unauthorized access, loss, or compromise.

The other options are not the second phase of PKI key/certificate life-cycle management, but rather other phases. The implementation phase is not a phase of PKI key/certificate life-cycle management, but rather a phase of PKI system deployment, where the PKI components and policies are installed and configured. The cancellation phase is not a phase of PKI key/certificate life-cycle management, but rather a possible outcome of the termination phase, where the key pair and the certificate are permanently revoked and deleted. The issued phase is not a phase of PKI key/certificate life-cycle management, but rather a possible outcome of the certification phase, where the CA verifies and approves the certificate request and issues the certificate to the end entity or the RA.