[RFC] Add Deposit/Withdraw to Tx Encoding

Authors: Youngjoon Lee Approvals (research): Marcin Pawlowski, Thomas Lavaur Approvals (engineering): Daniel Sanchez Quiros, Alex Cabeza Romero

Motivation

[1.1.0] Mantle Transaction Encoding does not cover channel deposit and withdraw operations, even though they have been already added to the [1.3.0] Mantle. This RFC proposes adding the encoding format of channel deposit and withdraw operations and their proofs to the [1.1.0] Mantle Transaction Encoding.

Proposal

We adapt the Mantle Transaction Encoding to include the Channel Deposit and Channel Withdraw operations as defined below:

  • CHANNEL_DEPOSIT
  • CHANNEL_WITHDRAW We add ChannelDeposit and ChannelWithdraw to Operations:
OpPayload = Transfer /
      ChannelInscribe /
            ChannelBlob /
            ChannelSetKeys /
+           ChannelDeposit /
+           ChannelWithdraw /
            SDPDeclare /
            SDPWithdraw /
            SDPActive /
            LeaderClaim

Then define the structures in Channel Operations:

    ChannelSetKeys = ChannelId KeyCount *Signer
    KeyCount       = Byte

+   ChannelDeposit = ChannelId Amount Metadata
+   Amount         = UINT64
+   Metadata       = UINT32 *BYTE

+   ChannelWithdraw = ChannelId Amount

   ChannelId = Hash32
   Parent    = Hash32
   Signer    = Ed25519PublicKey

Next we add ChannelWithdrawOpProof to Op Proofs:

OpsProofs  = *OpProof ; 1. Lenth must equal OpCount
                      ; 2. OpProof variant is derived from the corresponding Op.
                      ;    That is, type(OpProofs[i]) == ProofFor(Op[i])

OpProof  =  Ed25519SigProof /
            ZkSigProof /
            ZkAndEd25519SigsProof /
+           ChannelWithdrawOpProof /
            ProofOfClaimProof

Ed25519SigProof        = Ed25519Signature
ZkSigProof             = ZkSignature
ZkAndEd25519SigsProof  = ZkSignature Ed25519Signature
+ ChannelWithdrawOpProof = SignatureCount *IndexedEd25519Signature
ProofOfClaimProof      = Groth16

+ SignatureCount          = UINT16
+ ChannelKeyIndex         = UINT16
+ IndexedEd25519Signature = Ed25519Signature ChannelKeyIndex

Finally we extend the Common Structures with definition of UINT16:

; Zero-knowledge signature
ZkSignature = Groth16

; Cryptographic primitives
Groth16          = 128BYTE      ; pi_a (32) + pi_b (64) + pi_c (32)
ZkPublicKey      = FieldElement
Ed25519PublicKey = 32BYTE
Ed25519Signature = 64BYTE
FieldElement     = 32BYTE       ; BN254 field element (little-endian)
Hash32           = 32BYTE

 ; Primitive types
UINT64    = 8BYTE ; 64-bit unsigned integer, little-endian
UINT32    = 4BYTE ; 32-bit unsigned integer, little-endian
+ UINT16    = 2 BYTE ; 16-bit unsigned integer, little-endian

Byte      = OCTET

Justification

[1.1.0] Mantle Transaction Encoding does not cover channel deposit and withdraw operations, even though they have been already added to the [1.3.0] Mantle.

Specifications Update

  • [v1.2] Mantle Transaction Encoding