It's just a container 'cryptographic stuff'.Īnalogy time: saving a Word document. PEM can be used for many things: private keys, or certificates, or the text of an email that you want to encrypt or sign. So you want to save a private key in a file? PEM is a file format for storing general cryptgraphic information, but other file formats exist. Calling these 'just format differences' is fundamentally wrong, the software is doing a very different thing in the two cases (albeit to produce the same end-result transferring a file, or making a pretty document). pptx are different formats of Office documents. Let's try this: it's a bit like saying that http and ftp are just different formats for transferring files, or. I wish I could find a better way of explaining this, but I'm not sure I can without getting too technical. Ok, so DSA, RSA, and ECC are not different formats, they are completely different algorithms and are completely unrelated to each other.

Since both of your questions today have had the same underlying question, let's deal with it. Also note that ssh-keygen will only store Ed25519 keys in the new format, regardless of what flags you pass in. Seems pretty clear that this is just about the format of the file that's being produced. Ed25519 keys always use the new private key format. The new format has increased resistance to brute-force password cracking but is not supported by versions of OpenSSH prior to 6.5. o Causes ssh-keygen to save private keys using the new OpenSSH format rather than the more compatible PEM format. First off, here's the full man page entry for ssh-keygen -o from my machine ( ssh-keygen doesn't seem to have a version flag, but the man page is from February 17, 2016)

Ssh pem format