[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

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

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

Specifications Update

  • [v1.2] Mantle Transaction Encoding