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Which UUID version?

· 2 min read
Ayyaz Akhtar
Ayyaz Akhtar
Engineer @ Disney

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Universally Unique IDentifiers versions are defined by the RFC4122.

They are 5 different versions that have different implementations to generate Unique Identifiers.

v1 Time

Uses the CPU clock cycle to calculate a unique ID

v2 MAC

Uses the CPU clock cycle and MAC address to generate a unique ID.

v3 MD5

Uses a namespace value to salt the MD5 Hash (128 bits).

v4 Random

Uses Pseudo-random numbers to generate a unique ID.

v5 SHA-1

Uses a namespace value to salt the SHA-1 Hash (160 bits).

API​

Generally, a UUID library will expose all 5 versions and a few helper functions.

  • Version: Provides UUID RFC version
  • Parse: Convert UUID string to array of bytes
  • Stringify: Convert array of bytes to UUID string
  • Validate: Check if UUID is valid
  • Nil: All bits are set to 0
    • 00000000-0000-0000-0000-000000000000

Ranking​

Uniqueness

v1 👊 v2 👊 v4

v4 Random

v1 and v2 are similar, but the cpu cycle is predictable.

Hashing

v3 👊 v5

v5 SHA-1

v5 SHA-1 has a stronger encryption than v3 MD5.

Protected

v2 👊 v1 👊 v4 👊 v3 👊 v5

v5 SHA-1

v1 and v2 are similar, but the MAC address can make your system less secure.

Overall

v1 👊 v2 👊 v3 👊 v5 👊 v4

v4 Random

v4 is generally the best option in most use cases.