Bug: Compressed public key to the wrong address

[an-lee]

The original code

# https://github.com/q9f/eth.rb/blob/main/lib/eth/util.rb#L29
#
# Generates an Ethereum address from a given compressed or
# uncompressed binary or hexadecimal public key string.
#
# @param str [String] the public key to be converted.
# @return [Eth::Address] an Ethereum address.
def public_key_to_address(str)
  str = hex_to_bin str if hex? str
  bytes = keccak256(str[1..-1])[-20..-1]
  Address.new bin_to_prefixed_hex bytes
end

It seems that it doesn't handle the compressed public key right.

Example:

key = Eth::Key.new priv: '25ef37d1b525991c00b0feb44de32b72df35b20ddaae104f65bf09cae129a082'
Eth::Util.public_key_to_address(key.public_hex).to_s
# output: 0xa92Af1419c32A95c042A560E30bba1a6DcF1FD8e
Eth::Util.public_key_to_address(key.public_hex_compressed).to_s
# output: 0xa26bd09A48B9a83aC847Ed72275dEB0783a11c3E

Maybe we can fix it like this:

def public_key_to_address(str)
  str = hex_to_bin str if hex? str
+ str = Secp256k1::PublicKey.from_data(str).uncompressed
  bytes = keccak256(str[1..-1])[-20..-1]
  Address.new bin_to_prefixed_hex bytes
end

ref: https://github.com/etscrivner/rbsecp256k1/blob/master/documentation/public_key.md#from_datapublic_key_data

[q9f]

Good find. You are probably the first to use compressed public keys in the context of Ethereum. Most wallets and libraries don't support that.

Let me test this tomorrow.