Question 1

What is UUID v5?

Accepted Answer

UUID v5 is a name-based universally unique identifier defined in RFC 4122. It generates deterministic UUIDs using SHA-1 hash of a namespace UUID and a name string. The same namespace and name combination will always produce the same UUID, making it perfect for reproducible identifiers.

Question 2

Why choose UUID v5 over v3?

Accepted Answer

UUID v5 uses SHA-1 which is cryptographically stronger than MD5 used in v3. While both are deterministic and produce the same UUID for the same inputs, v5 offers better collision resistance and security. For all new applications requiring name-based UUIDs, v5 is the recommended choice.

Question 3

What's the difference between UUID v5 and v3?

Accepted Answer

Both v3 and v5 are name-based and deterministic, but they use different hash functions. v3 uses MD5 while v5 uses SHA-1. SHA-1 is cryptographically stronger than MD5, making v5 the recommended choice. They produce different UUIDs for the same inputs, so they're not interchangeable.

Question 4

Is UUID v5 secure?

Accepted Answer

UUID v5 uses SHA-1, which is stronger than MD5 but has known theoretical weaknesses. It's suitable for generating deterministic identifiers and is generally secure for most applications. However, don't use it for security-critical purposes like tokens, passwords, or cryptographic keys.

Version	Hash Function	Best Use Case
v3	MD5	Legacy name-based (upgrade to v5)
v4	None (Random)	General purpose, high randomness
v5	SHA-1	Name-based, reproducible identifiers

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What is UUID v5?

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