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Suppose I have multiple EC2 instances deployed with the same key-pair. The key-pair is used for SSH access and general troubleshooting. If one instance is compromised, do I need to be concerned about the key-pair allowing access to the other instances? What kind of cryptographic primitive is used for EC2 key-pairs?

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What kind of cryptographic primitive is used for EC2 key-pairs?

The keys that Amazon EC2 uses are 2048-bit SSH-2 RSA keys. They are asymmetric, "public key" pairs. The public key goes on the instance(s) you wish to authenticate to, and the private key stays with you.

If one instance is compromised, do I need to be concerned about the key-pair allowing access to the other instances?

No. Because only the public key is compromised, there is no concern; that's why it's a "public" key. Even when you authenticate to a compromised instance, the private key itself is not shared with the instance.

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  • Thanks, this makes things clear! – sdgfsdh Jan 18 at 16:52

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