Implement support for compressed public keys

[jakubgs]

Based off of status-im/status-go#1937 the handler needs to be able to accept compressed public key.

@Samyoul which compressed formats do we need to support? Just multiformat base58 encoded?

[Samyoul]

Thanks for creating this issue.

The specs for this are here https://github.com/status-im/specs/blob/master/docs/stable/2-account.md#public-key-serialization

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We actually support all multibase encoding formats. See https://github.com/multiformats/multibase

This may be useful https://github.com/multiformats/js-multibase

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Public key types:

• secp256k1 pks
• bls12-381 g1 pks
• bls12-381 g2 pks

But I've been told that we'd only use secp256k1 pks.

[jakubgs]

Looks like the secret sauce are multibase and secp256k1 JS libaries:

> s = 'zQ3shPyZJnxZK4Bwyx9QsaksNKDYTPmpwPvGSjMYVHoXHeEgB'
'zQ3shPyZJnxZK4Bwyx9QsaksNKDYTPmpwPvGSjMYVHoXHeEgB'
> b = multibase.decode(s)
<Buffer e7 01 02 26 1c 55 67 5e 55 ff 25 ed b5 0b 34 5c fb 3a 3f 35 f6 07 12 d2 51 cb aa ab 97 bd 50 05 4c 6e bc>
> secp256k1.publicKeyConvert(b.slice(2), compressed=false)
Uint8Array(65) [
    4,  38,  28,  85, 103,  94,  85, 255,  37, 237, 181,
   11,  52,  92, 251,  58,  63,  53, 246,   7,  18, 210,
   81, 203, 170, 171, 151, 189,  80,   5,  76, 110, 188,
   60, 212, 226,  34,   0, 198, 141, 175, 116, 147, 225,
  248, 218, 106,  25,  10, 104, 166, 113, 226, 211, 151,
  120,   9,  97,  36,  36, 199, 195, 136, 139, 198
]

[jakubgs]

And the other way around:

> k = "0x041c678bdeb6940df3e436cee76612ae6177f46e54e541fc024b572fafd9be89ba43612d6e26bba8f3961b5d379efe1fb031a718ea24936a83550086f4ba2c5c94"
'0x041c678bdeb6940df3e436cee76612ae6177f46e54e541fc024b572fafd9be89ba43612d6e26bba8f3961b5d379efe1fb031a718ea24936a83550086f4ba2c5c94'
> f = "f" + k.slice(2)
'f041c678bdeb6940df3e436cee76612ae6177f46e54e541fc024b572fafd9be89ba43612d6e26bba8f3961b5d379efe1fb031a718ea24936a83550086f4ba2c5c94'
> b = multibase.decode(f)
<Buffer 04 1c 67 8b de b6 94 0d f3 e4 36 ce e7 66 12 ae 61 77 f4 6e 54 e5 41 fc 02 4b 57 2f af d9 be 89 ba 43 61 2d 6e 26 bb a8 f3 96 1b 5d 37 9e fe 1f b0 31 ... 15 more bytes>
> c = secp256k1.publicKeyConvert(b)
Uint8Array(33) [
    2,  28, 103, 139, 222, 182, 148,  13,
  243, 228,  54, 206, 231, 102,  18, 174,
   97, 119, 244, 110,  84, 229,  65, 252,
    2,  75,  87,  47, 175, 217, 190, 137,
  186
]
> secp256k1MultifactorID = Buffer.from([231, 1])
> d = Buffer.concat([secp256k1MultifactorID, c])
<Buffer e7 01 02 1c 67 8b de b6 94 0d f3 e4 36 ce e7 66 12 ae 61 77 f4 6e 54 e5 41 fc 02 4b 57 2f af d9 be 89 ba>
> multibase.encode('base58btc', d).toString()
'zQ3shPKfkQPeJdWMrXMtSfCFHhDR9gck99GsYt4Er3yvHxT2Z'

[jakubgs]

This post was a good resource: status-im/status-go#1937 (comment)

[Samyoul]

I'm please you found it helpful, I always try share the information I learn to make the learning curve of anyone else to be less steep than mine 😆