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RSA encryption is still very widely used (for example SSH keys with 4096 bit RSA keys). To call it obsolete would need solid basis of argument, I think. Perhaps

RSA encryption is still very widely used (for example SSH keys with 4096 bit RSA keys). To call it obsolete would need solid basis of argument, I think. Perhaps you mean that specific implementation or way of implementing it?

tialaramex 2y ago
> RSA encryption is still very widely used (for example SSH keys with 4096 bit RSA keys) That's not RSA encryption. Which is fascinating, and my cough got even worse and I have a fever and my demo worked in the presentation anyway, and so I won't be doing any further productive work today... SSHv2 (You don't use SSHv1, if you're younger you may never have used SSHv1) goes roughly like this 1. SSH client connects to SSH server (TCP stuff happens) they agree that they both speak SSHv2 3. SSH client says it can do certain types of cryptographic operation, the server says what it is willing to do, they should overlap or else no progress can be made. 4. A Diffie Hellman Key Exchange is performed based on the shared information from above, now the Client and the Server know a set of fresh unique keys for this session, all further data is encrypted with a symmetric algorithm using these keys. 5a. Now the client should explain how it intends to authenticate as a specific user. It probably wants to prove it has a private key corresponding to a public key that the server already knows (but it could use old-fashioned Unix passwords if that's enabled). 5a. For pubkey auth, the client says "I can prove I have the private key for this 4096 bit RSA key you know" 6. The server can say either "Fine, I know that RSA key, prove it" or "No good, what else can you do?" 7. Assuming the server said "Fine" the client performs RSA signing not encryption to demonstrate that it does have the private key. The signed message is a witness to the above unique conversation and thus cannot be re-played or re-used for any purpose.

tialaramex 2y ago

> RSA encryption is still very widely used (for example SSH keys with 4096 bit RSA keys) That's not RSA encryption. Which is fascinating, and my cough got even worse and I have a fever and my demo worked in the presentation anyway, and so I won't be doing any further productive work today... SSHv2 (You don't use SSHv1, if you're younger you may never have used SSHv1) goes roughly like this 1. SSH client connects to SSH server (TCP stuff happens) they agree that they both speak SSHv2 3. SSH client says it can do certain types of cryptographic operation, the server says what it is willing to do, they should overlap or else no progress can be made. 4. A Diffie Hellman Key Exchange is performed based on the shared information from above, now the Client and the Server know a set of fresh unique keys for this session, all further data is encrypted with a symmetric algorithm using these keys. 5a. Now the client should explain how it intends to authenticate as a specific user. It probably wants to prove it has a private key corresponding to a public key that the server already knows (but it could use old-fashioned Unix passwords if that's enabled). 5a. For pubkey auth, the client says "I can prove I have the private key for this 4096 bit RSA key you know" 6. The server can say either "Fine, I know that RSA key, prove it" or "No good, what else can you do?" 7. Assuming the server said "Fine" the client performs RSA signing not encryption to demonstrate that it does have the private key. The signed message is a witness to the above unique conversation and thus cannot be re-played or re-used for any purpose.