= OpenSSH Key Structure Guide
brent saner <bts@square-r00t.net>, https://r00t2.io
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== 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 https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.key[the OpenSSH source tree's `PROTOCOL.key`^], which is a little lacking.

== Basic Introduction
=== Legacy
==== Private Keys

In OpenSSH pre-7.8, private keys are stored in their respective PEM encodingfootnote:[https://datatracker.ietf.org/doc/html/rfc7468] with no modification. These legacy private keys should be entirely usable by OpenSSL/LibreSSL/GnuTLS etc. natively with no conversion necessary.

==== 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, Base64footnote:[https://datatracker.ietf.org/doc/html/rfc4648]-encoded
C:: The key's comment

The structures specified in the breakdowns later in this document describe the _decoded_ version of *B* *_only_*.


=== New "v1" Format
==== Private Keys
==== Public Keys

== Keytype-Specific Breakdowns
include::rsa/main.adoc[]

=== ED25519