Guid Smash
guidsmash.com
Guid Smash
1–10 of 72 posts
Re: Guid Smash
#2Nice experiment. Is the code available somewhere?
Re: Guid Smash
#3Note that this only considers UUIDv4, the random UUID. Other forms can generate UUIDs that are much closer together. For UUIDv7, UUIDs generated within the same millisecond will have identical 48 bit prefixes (or up to 60 when the monotonic counter from section 6.2 is used).
https://www.rfc-editor.org/rfc/rfc9562.html#monotonicity_cou...
Re: Guid Smash
#4Instead of picking a target UUID and evaluating new UUIDs against it, a better experiment would be finding duplicates in all the UUIDs you have generated.
This plays nicely with the birthday paradox.
Re: Guid Smash
#5> The chances of generating two GUIDs that are the same is astronomically small.
> The odds are 1 in 2^122 — that’s approximately 1 in 5,000,000,000,000,000,000,000,000,000,000,000,00.
This is true if you only generate two GUIDs, but if you generate very many GUIDs, the chance of generating two identical ones between any of them increases. E.g. if you generate 2^61 GUIDs, you have about a 1 in 2 chance of a collision, due to the birthday paradox.
2^61 is still a very large number of course, but much more feasible to reach than 2^122 when doing a collision attack. This is the reason that cryptographic hashes are typically 256 bits or more (to make the cost of collision attacks >= 2^128).
Re: Guid Smash
#6> The chances of generating two GUIDs that are the same is astronomically small. > The odds are 1 in 2^122 — that’s approximately 1 in 5,000,000,000,000,000,000,000,000,000,000,000,00. This is true if you only generate two GUIDs, but if you generate very many GUIDs, the chance of generating two identical ones between any of them increases. E.g. if you generate 2^61 GUIDs, you have about a 1 in 2 chance of a collision…
2^61 isn't even that large, well within the compute budget of mere mortals.
Re: Guid Smash
#7This is the chance that given a specific guid, that you'll find a collision for it. Utterly minuscule chance. However birthday paradox controls, if you generate 2^62.60 guids the chance that you've generated a collision is around 99%. Still enormously unlikely, but way smaller than 2^122.
At a rate of comparing 400,000 guids per second, you have a 99% chance of seeing a collision within the next 553,750 years.
Re: Guid Smash
#8Note that this only considers UUIDv4, the random UUID. Other forms can generate UUIDs that are much closer together. For UUIDv7, UUIDs generated within the same millisecond will have identical 48 bit prefixes (or up to 60 when the monotonic counter from section 6.2 is used). https://www.rfc-editor.org/rfc/rfc9562.html#monotonicity_cou...
You need to be generating >100M of them within the same millisecond before even remembering that collisions can theoretically happen.
Re: Guid Smash
#9Note that this only considers UUIDv4, the random UUID. Other forms can generate UUIDs that are much closer together. For UUIDv7, UUIDs generated within the same millisecond will have identical 48 bit prefixes (or up to 60 when the monotonic counter from section 6.2 is used). https://www.rfc-editor.org/rfc/rfc9562.html#monotonicity_cou...
You need to be generating >100M of them within the same millisecond before even remembering that collisions can theoretically happen.
>You
The entire universe. Else it's not universally unique.
Re: Guid Smash
#10> The chances of generating two GUIDs that are the same is astronomically small. > The odds are 1 in 2^122 — that’s approximately 1 in 5,000,000,000,000,000,000,000,000,000,000,000,00. This is true if you only generate two GUIDs, but if you generate very many GUIDs, the chance of generating two identical ones between any of them increases. E.g. if you generate 2^61 GUIDs, you have about a 1 in 2 chance of a collision…
* not the birthday paradox, but the birthday bound.