RFC 4122 Cryptographic UUID / GUID v4 Generator

A standard UUID v4 is represented as a 36-character string containing 32 hexadecimal digits and 4 hyphens, organized into five distinct groups:

`` xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx ``

• Total Entropy: 122 bits of cryptographically secure random entropy.
• Version Nibble (`4`): The 13th hexadecimal character is fixed to 4, identifying the string as a Version 4 (randomly generated) UUID.
• Variant Bits (`y`): The 17th character is restricted to 8, 9, a, or b (binary 10xx), denoting compliance with the RFC 4122 / Leach-Salz variant standard.

Because a UUID v4 contains $122$ bits of pure entropy, the total number of possible unique identifiers is $2^{122} \approx 5.3 \times 10^{36}$ (5.3 undecillion):

• Collision Math: To have a one-in-a-billion ($10^{-9}$) chance of generating a single collision, a system would need to generate over 103 trillion UUIDs.
• Distributed Systems: Multiple independent database nodes can generate UUID v4 primary keys concurrently with zero coordination and zero collision risk.