1.5 KiB
OpenSSH Key Structure Guide
1. Purpose
This document attempts to present a much more detailed, thorough, and easily-understood form of the key formats used by OpenSSH. The extent of those formats' canonical documentation is the OpenSSH source tree’s PROTOCOL.key, which is a little lacking.
2. Basic Introduction
2.1. Legacy
2.1.1. Private Keys
In OpenSSH pre-7.8, private keys are stored in their respective PEM encoding[1] with no modification. These legacy private keys should be entirely usable by OpenSSL/LibreSSL/GnuTLS etc. natively with no conversion necessary.
2.1.2. Public Keys
Each public key file (*.pub) is written out in the following format:
A B C
Where:
- A
-
The key type (e.g.
ssh-rsa,ssh-ed25519, etc.) - B
-
The public key itself, Base64[2]-encoded
- C
-
The key’s comment
The structures specified in the breakdowns later in this document describe the decoded version of B only.
3. Keytype-Specific Breakdowns
Unresolved directive in <stdin> - include::rsa/main.adoc[]