Re: [DNSOP] Specification of DNSKEY "Private-key-format"

[Viktor Dukhovni <[e-mail]>]

On Thu, Aug 29, 2019 at 06:25:02PM +0530, Mukund Sivaraman wrote:
> A tool such as BIND's dnssec-keygen generates the following formatted
> private keys:
> 
> [muks@naina ~]$ cat Kexample.org.+008+10638.private
> Private-key-format: v1.3
> Algorithm: 8 (RSASHA256)
> Modulus: [...]
> PublicExponent: [...]
> PrivateExponent: [...]
> Prime1: [...]
> Prime2: [...]
> Exponent1: [...]
> Exponent2: [...]
> Coefficient: [...]

Compare the above with:

    $ openssl genrsa 512 2>/dev/null | openssl rsa -text -noout | egrep -v ':..:'
    RSA Private-Key: (512 bit, 2 primes)
    modulus:
    publicExponent: 65537 (0x10001)
    privateExponent:
    prime1:
    prime2:
    exponent1:
    exponent2:
    coefficient:

And it becomes clear that what you're seeing is a sequence of tagged
base64 encodings of the BIGNUM elements of the CRT form of an RSA
private key.

> Created: [...]
> Publish: 20190829125147
> Activate: 20190829125147

Plus some additional metadata.

> I have looked around for a specification for this format, but I fail to
> find one. Where is this specified? Has it ever been described in some
> document?

This looks like an ad-hoc format, specific to dnssec-keygen and
friends.  In particular "Publish:" and "Activate:" are not part of
the key per-se and are rather related to the DNSSEC key lifecycle.

-- 
	Viktor.