Validating Elliptic curve signatures in Erlang

gistfile1.txt

% check against sigs generated at https://8gwifi.org/ecsignverify.jsp
% ideas from https://github.com/0x6e6562/otp_ecc/blob/master/src/otp_ecc.erl

Erlang/OTP 19 [erts-8.3] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false]

Eshell V8.3  (abort with ^G)
1> PublicBin = <<"-----BEGIN PUBLIC KEY-----
1> MFYwEAYHKoZIzj0CAQYFK4EEAAoDQgAElMlYUyrmL2UJV7hlug5/p1eeoOmXptgM
1> 3K4h8opBX3rGSFHhOIA2Yw1DBKCXKC8cGnNEUsmCunslB1OaYcFinw==
1> -----END PUBLIC KEY-----
1> ">>.
<<"-----BEGIN PUBLIC KEY-----\nMFYwEAYHKoZIzj0CAQYFK4EEAAoDQgAElMlYUyrmL2UJV7hlug5/p1eeoOmXptgM\n3K4h8opBX3rGSFHhOIA2Yw1D"...>>

2> [PublicPemEntry] = public_key:pem_decode(PublicBin), PublicKey = public_key:pem_entry_decode(PublicPemEntry).
{{'ECPoint',<<4,148,201,88,83,42,230,47,101,9,87,184,101,
              186,14,127,167,87,158,160,233,151,166,216,
              12,220,...>>},
 {namedCurve,{1,3,132,0,10}}}
 
3> Sig = <<"MEQCIARxV3Lmms1vLhdlShi6qyfA+wu7fWrttekksOk/o/FbAiA0Y5/yYI4yAuXKqO/zrQjkju+hMfGw8Jus8V5b/hVTLQ==">>.
<<"MEQCIARxV3Lmms1vLhdlShi6qyfA+wu7fWrttekksOk/o/FbAiA0Y5/yYI4yAuXKqO/zrQjkju+hMfGw8Jus8V5b/hVTLQ==">>

4> public_key:verify(<<"a">>, sha256, base64:decode(Sig), PublicKey).
true

5> public_key:verify(<<"aa">>, sha256, base64:decode(Sig), PublicKey).
false

6> f(Sig).
ok

7> Sig = <<"MEUCIQCFjP4VGwDmCcGLbPWUtJdY67TuaohaNipgbBiGriw1GQIgERxAwDiVQs3c6hy4beMaz5BDVk12fr3mf3gScKFDQYA=">>.
<<"MEUCIQCFjP4VGwDmCcGLbPWUtJdY67TuaohaNipgbBiGriw1GQIgERxAwDiVQs3c6hy4beMaz5BDVk12fr3mf3gScKFDQYA=">>

8> public_key:verify(<<"aa">>, sha256, base64:decode(Sig), PublicKey).
true