What is Hash?
A hash is a fixed-size string or number generated from input data of any size, created using a hash function. This function ensures that even a tiny change in the input data results in a significantly different hash value. In the context of cybersecurity and identity and access management (IAM), hashes play a crucial role in ensuring data integrity and security.
Hash functions are deterministic, meaning the same input always produces the same hash. They are designed for fast computation, allowing quick generation of hash values. A crucial feature is pre-image resistance, which makes it infeasible to reverse the hash function and retrieve the original input from its hash value. Furthermore, even a small change in the input should produce a substantially different hash, and hash functions are collision-resistant, making it extremely difficult to find two different inputs that produce the same hash value.
Password Storage
In password storage, systems use hashes instead of storing plaintext passwords. When a user logs in, the system hashes the provided password and compares it to the stored hash. To enhance security, a unique value called a "salt" is added to the password before hashing to defend against rainbow table attacks.
Data Integrity
Hashes also ensure data integrity by verifying that data has not been tampered with. For example, file integrity checks use hashes to verify that files remain unaltered. Digital signatures and checksums also employ hash functions to verify data authenticity and integrity.
Digital Signatures
Digital signatures use hashes to create a secure method for verifying messages. A hash of a message is encrypted with a private key to create a digital signature, which can be verified by decrypting it with the corresponding public key and comparing it to a newly generated hash of the message.
Message Authentication Codes (MACs)
In message authentication codes (MACs), hash functions verify the integrity and authenticity of a message. A MAC is created by combining the message with a secret key and hashing the result. In the realm of blockchain and cryptocurrencies, hash functions ensure the integrity and immutability of transactions. Each block contains the hash of the previous block, linking them together.
Certificates and Public Key Infrastructure (PKI)
Certificates and Public Key Infrastructure (PKI) use hashes to ensure the integrity and authenticity of public keys. Certificate Authorities (CAs) sign certificates using hashed values. Hashes can also be used to manage and secure tokens in various authentication protocols, such as OAuth and JWT.
Popular Hash Functions
Popular hash functions include MD5 (Message Digest Algorithm 5), which was once widely used but is now considered broken and unsuitable due to vulnerabilities. SHA-1 (Secure Hash Algorithm 1) is also considered outdated and vulnerable. More secure alternatives are SHA-256 and SHA-3, which are part of the SHA-2 and SHA-3 families and offer stronger security, making them widely used in modern applications. Additionally, bcrypt, scrypt, and Argon2 are specifically designed for securely hashing passwords, incorporating salting and multiple iterations to thwart attacks.
