What are the key principles of cryptography in information security?

Cryptography, in the realm of information security, relies on several key principles to ensure the confidentiality, integrity, authenticity, and non-repudiation of data. Here's a technical breakdown of these principles:

1. Confidentiality: The primary goal of confidentiality is to ensure that unauthorized entities cannot access the contents of encrypted data. This is typically achieved through encryption, where plaintext data is transformed into ciphertext using cryptographic algorithms and keys. Only authorized parties possessing the corresponding decryption keys should be able to reverse the process and access the original plaintext.
2. Encryption Algorithms: Cryptographic algorithms form the backbone of encryption schemes. These algorithms are mathematical functions designed to scramble plaintext data into ciphertext in such a way that it becomes computationally infeasible for unauthorized parties to derive the original plaintext without the decryption key. Common encryption algorithms include Advanced Encryption Standard (AES), RSA, and Elliptic Curve Cryptography (ECC).
3. Key Management: Cryptographic keys are essential components of encryption systems. They are used to encrypt and decrypt data securely. Effective key management involves generating, distributing, storing, and revoking keys in a secure and organized manner. Key management practices include key generation using secure random number generators, key distribution using secure channels, and key storage in protected environments such as hardware security modules (HSMs).
4. Integrity: Integrity ensures that data remains unchanged and unaltered during storage, transmission, or processing. Cryptographic hash functions play a crucial role in maintaining data integrity. These functions generate fixed-size hash values (digests) from input data, such that even a small change in the input results in a significantly different output. By comparing hash values before and after data transmission or storage, recipients can verify the integrity of the data.
5. Hash Functions: Cryptographic hash functions are one-way functions that produce a fixed-size output (hash value) from an arbitrary-length input. They possess several key properties, including collision resistance (it is computationally infeasible to find two different inputs that produce the same hash value), pre-image resistance (given a hash value, it is computationally infeasible to find the original input), and second pre-image resistance (given an input, it is computationally infeasible to find a different input that produces the same hash value). Examples of cryptographic hash functions include SHA-256 and SHA-3.
6. Authentication: Authentication ensures that the identities of communicating parties are verified and that data exchanges occur between trusted entities. Digital signatures are commonly used for authentication in cryptographic systems. A digital signature is created using a private key and can be verified using the corresponding public key. It provides proof of the origin, identity, and integrity of the signed data. Public key infrastructure (PKI) frameworks facilitate the management and distribution of digital certificates, which contain public keys and other identity information.
7. Non-Repudiation: Non-repudiation prevents individuals from denying their actions or transactions. Digital signatures also play a crucial role in achieving non-repudiation. When a user digitally signs a document or message using their private key, it provides evidence that the user sent the message and that the message has not been altered since it was signed. This evidence can be independently verified by third parties using the signer's public key, thereby preventing the signer from denying their involvement.