Remove unnecessary "Random" command when signing.

[ke6jjj]

It is not neccessary to invoke the "GenRandom" command before requesting an ECDSA signature. This command does not generate the nonce (random value "k") that is required for ECDSA -- that is performed internally by the ECC508/ECC608 and always has been.

By removing this unnecessary command it should be possible to generate signatures in less time than before.

Status

I tested signature generation with this branch and confirmed that it generates a correct signature for the message <<"hello">> using the ECC608 on an sidetable_v1 OG unit.

[ke6jjj]

Round-trip test procedure

You can use the following round-trip test to confirm that this branch produces usable, correct signatures.

Prerequisites

• A development machine with an ATECC608 attached via I2C.
• Erlang/OTP
• A copy of this repository.
• A copy of the libp2p-crypto repository.

Steps

1. Check out this test branch of the ecc508 repository
2. Invoke ./rebar3 shell (the rebar3 executable in this repository is quite old, consider copying rebar3 from elsewhere)
3. Start up the process and generate a signature on the message <<"hello">>

Erlang/OTP 24 [erts-12.1.5] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1]

Eshell V12.1.5  (abort with ^G)
1> {ok, Pid} = ecc508:start_link().
{ok,<0.229.0>}
2> ecc508:wake(Pid), {ok, Sig} = ecc508:sign(Pid, 0, <<"hello">>).
{ok,<<48,...>>}
3> rp(Sig).
<<SAVE-THIS>>

4. Save the signature bytes and shut down the shell.
5. Obtain the b58 form of the ECC608 public key. Example: 112VYECRxdyUixsN3KyTMdJaNdGGNF6UARwS5Pkyi86xoiBkSyLU
6. Invoke ./rebar3 shell in the libp2p-crypto repository

Erlang/OTP 24 [erts-12.1.5] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1]

Eshell V12.1.5  (abort with ^G)
1> Sig = <<SAVED-SIGNATURE-ABOVE>>.
<<48,...>>
2> PubKey = libp2p_crypto:b58_to_pubkey("112VYECRxdyUixsN3KyTMdJaNdGGNF6UARwS5Pkyi86xoiBkSyLU").
{ecc_compact,{{'ECPoint',<<4,196,126,252,69,98,75,22,54,
                           8,245,151,245,120,179,249,158,
                           197,6,96,75,159,202,15,...>>},
              {namedCurve,{1,2,840,10045,3,1,7}}}}
3> libp2p_crypto:verify(<<"hello">>, Sig, PubKey).
true