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What's the impact to something like git that makes extensive use of SHA-1? In their example they've created two PDFs with the same SHA-1. Could I replace the blob in a git repo with the "bad" version of a file if it matches the SHA-1?
What's the impact to something like git that makes extensive use of SHA-1? In their example they've created two PDFs with the same SHA-1. Could I replace the blob in a git repo with the "bad" version of a file if it matches the SHA-1?
Here's a good blog about how SHA-1 works: http://www.metamorphosite.com/one-way-hash-encryption-sha1-d... . The biggest risk I see with this is how torrents are affected: https://en.wikipedia.org/wiki/Torrent_poisoning There's also a problem with git, but I don't see it being that as susceptible as torrents: http://stackoverflow.com/a/34599081/6448137
This makes it technically possible to get a backdoored linux repo with the same commit hash.
EDIT: this is wrong, it's not a second pre-image attack only a collision attack. That is, you can create 2 git repositories with the same commit hash, but not a git repo that matches an already existing repo. In other words, you can create 2 things with the same hash, but can't control what that hash actually is.
You might be able to fashion 2 commits to the linux repo with the same hash but a different modification though.
What's the impact to something like git that makes extensive use of SHA-1? In their example they've created two PDFs with the same SHA-1. Could I replace the blob in a git repo with the "bad" version of a file if it matches the SHA-1?
>How is GIT affected? GIT strongly relies on SHA-1 for the identification and integrity checking of all file objects and commits. It is essentially possible to create two GIT repositories with the same head commit hash and different contents, say a benign source code and a backdoored one. An attacker could potentially selectively serve either repository to targeted users. This will require attackers to compute their own collision.
Here's a good blog about how SHA-1 works: http://www.metamorphosite.com/one-way-hash-encryption-sha1-d... . The biggest risk I see with this is how torrents are affected: https://en.wikipedia.org/wiki/Torrent_poisoning There's also a problem with git, but I don't see it being that as susceptible as torrents: http://stackoverflow.com/a/34599081/6448137
What about git? This makes it technically possible to get a backdoored linux repo with the same commit hash. EDIT: this is wrong, it's not a second pre-image attack only a collision attack. That is, you can create 2 git repositories with the same commit hash, but not a git repo that matches an already existing repo. In other words, you can create 2 things with the same hash, but can't control what that hash actually…
Anyone have back of the envelope calculations for the cost of the CPU and GPU time?
On the shattered webpage: This attack required over 9,223,372,036,854,775,808 SHA1 computations. This took the equivalent processing power as 6,500 years of single-CPU computations and 110 years of single-GPU computations.
>Nine quintillion computations; 6,500 years of CPU; 110 years of GPU Is there a rough calculation in terms of today's $$$ cost to implement the attack?
> Using a p2.16xlarge instance, featuring 16 K80 GPUs and nominally costing US 14.4 per hour would cost US 560 K for the necessary 71 device years
Here's a good blog about how SHA-1 works: http://www.metamorphosite.com/one-way-hash-encryption-sha1-d... . The biggest risk I see with this is how torrents are affected: https://en.wikipedia.org/wiki/Torrent_poisoning There's also a problem with git, but I don't see it being that as susceptible as torrents: http://stackoverflow.com/a/34599081/6448137
What about git? This makes it technically possible to get a backdoored linux repo with the same commit hash. EDIT: this is wrong, it's not a second pre-image attack only a collision attack. That is, you can create 2 git repositories with the same commit hash, but not a git repo that matches an already existing repo. In other words, you can create 2 things with the same hash, but can't control what that hash actually…
ORIGINALLY (INCORRECT): Git commit hashes were at least never intended as a form of authentication. That's why git has commit signing. That said, they list GPG signatures as one of the things affected by SHA1 brokenness, so maybe even that's not enough? I don't know enough about how git commit signing or GPG works to tell.
>Nine quintillion computations; 6,500 years of CPU; 110 years of GPU Is there a rough calculation in terms of today's $$$ cost to implement the attack?