[Cryptography] Blockchain without proof of work

[Phillip Hallam-Baker]

On Fri, Jan 4, 2019 at 7:16 PM Patrick Chkoreff <pc at fexl.com> wrote:

> Phillip Hallam-Baker wrote on 1/3/19 1:29 PM:
>
> > UDF=KD25H-GSNE2-JVVJE-RXTMA-7VAWT
> > UDF=KCOO3-EKPAG-FKYFC-O2B2N-O3UUA
> > UDF=KBR3A-RQLV7-SMB6X-6OB7X-JMBNT
>
> Ooh, I've tagged this email as "Later" so I can go back to that.  How
> will I go about verifying those when the secrets are divulged?  (Pardon
> me if I haven't been paying attention in class here.)
>

OK so I have decided to make a few changes to the structure here so the
values will change.

Let us say that m = "Konrad is a Kompromised agent".
first choose a random key kt = P (0xB0 || rand (512), 125)
(where P is the presentation/truncation function using Base32 putting in
dashes every 5 characters and truncating to 125 bits)

We use SHA-2-512 to construct a Keyed UDF, so HKDF(), H(), HMAC() are
functions all using that as the base digest:

k = HKDF (kt, 512)
f = HMAC (k, ct || ':' || H(m))
udf = P((v || f), 125)

Where v is simply a tag to identify the fingerprint type and ct is the IANA
content type

So the core here is that we have a fingerprint of the data that can only be
verified if the key kt is known. Since this is a keyed digest, we are using
an HMAC for the purpose.

I have pushed out the code to GitHub but I need to clean it up a bit. The
version prefixes have been chosen so that the version number shows the
fingerprint type. A SHA-2 fingerprint will always start with an M
(Merkle-Damguard) and SHA-3 will always start with an S (Spongeworthy).
Random numbers will always start with R and I had chosen K for Keyed hash.

It since occurs to me that I should probably use K for actual Keys so maybe
I need to move the prefixes about.
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