Question 1

How can you identify the type of a cryptographic hash?

Accepted Answer

Hash types can often be identified by their length and character set. MD5 produces 32 hex characters, SHA-1 produces 40, SHA-256 produces 64, and SHA-512 produces 128. Bcrypt hashes start with $2b$ or $2a$ and are 60 characters long. Argon2 hashes begin with $argon2id$. Context also matters — password databases, file checksums, and digital signatures each favor certain algorithms.

Question 2

Why are some hash algorithms considered insecure?

Accepted Answer

MD5 and SHA-1 are considered cryptographically broken because researchers have demonstrated practical collision attacks — producing two different inputs with the same hash. This undermines their use in digital signatures and integrity verification. For password storage, unsalted fast hashes like MD5 and SHA-256 are vulnerable to rainbow table and brute-force attacks, which is why slow, salted algorithms like bcrypt and Argon2 are recommended.

Hash Identifier

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