Module: Mpp::Methods::Tempo::Attribution

Defined in:
lib/mpp/methods/tempo/attribution.rb

Defined Under Namespace

Classes: DecodedMemo

Constant Summary collapse

VERSION = 
0x01
ANONYMOUS = 
"\x00" * 10

Class Method Summary collapse

Class Method Details

.decode(memo) ⇒ Object

Decode an MPP attribution memo.



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# File 'lib/mpp/methods/tempo/attribution.rb', line 94

def decode(memo)
  return nil unless mpp_memo?(memo)

  begin
    version = memo[10, 2].to_i(16)
    server_fingerprint = "0x#{memo[12, 20]}"
    client_hex = memo[32, 20]
    nonce = "0x#{memo[52..]}"

    client_bytes = [client_hex].pack("H*")
    client_fingerprint = (client_bytes == ANONYMOUS.b) ? nil : "0x#{client_hex}"
  rescue ArgumentError
    return nil
  end

  DecodedMemo.new(
    version: version,
    server_fingerprint: server_fingerprint,
    client_fingerprint: client_fingerprint,
    nonce: nonce
  )
end

.encode(server_id:, client_id: nil, challenge_id: nil) ⇒ Object

Encode an MPP attribution memo (32 bytes).

Byte Layout:

0..3:   TAG = keccak256("mpp")[0:4]
4:      version (0x01)
5..14:  serverId fingerprint
15..24: clientId fingerprint or zeros
25..31: random nonce


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# File 'lib/mpp/methods/tempo/attribution.rb', line 38

def encode(server_id:, client_id: nil, challenge_id: nil)
  buf = "\x00".b * 32
  buf[0, 4] = tag
  buf[4] = [VERSION].pack("C")
  buf[5, 10] = fingerprint(server_id)
  buf[15, 10] = client_id ? fingerprint(client_id) : ANONYMOUS.b
  buf[25, 7] = if challenge_id
    keccak256(challenge_id.encode(Encoding::UTF_8))[0, 7]
  else
    SecureRandom.random_bytes(7)
  end
  "0x#{buf.unpack1("H*")}"
end

.fingerprint(value) ⇒ Object 



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# File 'lib/mpp/methods/tempo/attribution.rb', line 26

def fingerprint(value)
  keccak256(value.encode(Encoding::UTF_8))[0, 10]
end

.keccak256(data) ⇒ Object

Ethereum Keccak-256. SHA3-256 is not a substitute (different padding).



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# File 'lib/mpp/methods/tempo/attribution.rb', line 17

def keccak256(data)
  Digest::Keccak.digest(data, 256)
end

.mpp_memo?(memo) ⇒ Boolean

Check if a memo is an MPP attribution memo.

Returns:

  • (Boolean) 


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# File 'lib/mpp/methods/tempo/attribution.rb', line 53

def mpp_memo?(memo)
  return false unless memo.length == 66

  begin
    memo_tag = [memo[2, 8]].pack("H*")
    memo_version = memo[10, 2].to_i(16)
  rescue ArgumentError
    return false
  end
  memo_tag == tag && memo_version == VERSION
end

.tag ⇒ Object

Compute TAG = keccak256("mpp")[0:4]



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# File 'lib/mpp/methods/tempo/attribution.rb', line 22

def tag
  @tag ||= keccak256("mpp".b)[0, 4]
end

.verify_challenge_binding(memo, challenge_id) ⇒ Object

Verify challenge-bound nonce in memo.



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# File 'lib/mpp/methods/tempo/attribution.rb', line 78

def verify_challenge_binding(memo, challenge_id)
  return false unless challenge_id
  return false unless mpp_memo?(memo)

  begin
    memo_nonce = [memo[52, 14]].pack("H*")
  rescue ArgumentError
    return false
  end
  memo_nonce == keccak256(challenge_id.encode(Encoding::UTF_8))[0, 7]
end

.verify_server(memo, server_id) ⇒ Object

Verify server fingerprint in memo.



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# File 'lib/mpp/methods/tempo/attribution.rb', line 66

def verify_server(memo, server_id)
  return false unless mpp_memo?(memo)

  begin
    memo_server = [memo[12, 20]].pack("H*")
  rescue ArgumentError
    return false
  end
  memo_server == fingerprint(server_id)
end