SOURCE-LEVEL RESULT • TRANSACTION VALIDATION

VTA Transaction Validation Audit

We now trace the actual VTA source from transaction structure checks to mempool input checks and the consensus input-validation interface. The findings below are limited to what the public source exposes.

VERIFIED IN CODE

Transaction structure

CheckTransaction() rejects empty inputs/outputs, oversize transactions, negative outputs, excessive outputs, duplicate inputs and invalid non-coinbase null prevouts.

VERIFIED IN CODE

Double-spend gate

AcceptToMemoryPool() checks HaveInputs(tx) and rejects inputs that are already spent.

VERIFIED IN CODE

Consensus validation interface

main.h explicitly defines CheckInputs() as checking inputs for double spends, scripts/signatures and amounts, without modifying the UTXO set.

1. Transaction sanity checks

These checks happen before the transaction is accepted into the mempool. They protect basic transaction invariants and reject malformed or economically invalid output values.

Rule
VTA source evidence
Status
Inputs present
tx.vin.empty() → bad-txns-vin-empty
Verified
Outputs present
tx.vout.empty() → bad-txns-vout-empty
Verified
Transaction size
Serialized size is checked against MAX_BLOCK_SIZE.
Verified
Output amount range
Rejects negative outputs, outputs above MAX_MONEY, and totals outside MoneyRange().
Verified
Duplicate inputs
A set<COutPoint> detects repeated prevouts and rejects them.
Verified
Coinbase rules
Coinbase scriptSig length is constrained to 2–100 bytes; non-coinbase null prevouts are rejected.
Verified
Primary source: VirtaCoinProject/src/main.cpp, CheckTransaction().

2. Double-spend protection path

Incoming transaction
→
CheckTransaction()
→
mempool conflict check
→
HaveInputs(tx)
→
CheckInputs()

In AcceptToMemoryPool(), VTA first checks whether the transaction already exists in the pool, then checks for conflicts on each input outpoint. If view.HaveInputs(tx) is false, the transaction is rejected with bad-txns-inputs-spent.

This is direct source evidence that the mempool admission path contains a spent-input/conflict gate.

Source: main.cpp, AcceptToMemoryPool().

3. CheckInputs contract

The VTA main.h interface describes CheckInputs() as checking whether all transaction inputs are valid, specifically including no double spends, scripts & signatures, and amounts. It also states that this function does not modify the UTXO set.

The same header exposes UpdateCoins() separately to apply a valid transaction's effects to the UTXO view. This separation is important for auditing: validation and state mutation are represented as separate operations.

Verified source architecture.

Primary source: VirtaCoinProject/src/main.h, declarations around CheckInputs() and UpdateCoins().

4. Script/signature validation interface

Component
Source evidence
Status
VerifySignature()
main.h declares VerifySignature(const CCoins&, const CTransaction&, ...).
Verified interface
CScriptCheck
main.h defines a script-check object carrying the previous output script, spending transaction, input index, flags and hash type.
Verified interface
AreInputsStandard()
VTA evaluates input script forms and rejects non-standard P2SH/input structures in the main-network mempool path.
Verified
Primary sources: main.h and main.cpp.

5. UTXO/state transition

main.h exposes UpdateCoins() as the function that applies a transaction's effects to the UTXO view and records undo information. The source also exposes block/transaction database verification and block-processing functions.

This gives us a clean audit boundary:

  • Validate: determine whether the transaction is acceptable.
  • Apply: update the UTXO state only after validation.
  • Undo: preserve undo information for state restoration.
Primary source: main.h.

6. Banking/payment relevance

CODE EVIDENCE

Value integrity

Negative, excessive and out-of-range aggregate outputs are rejected at transaction validation.

CODE EVIDENCE

Spend integrity

Spent-input conflicts are explicitly checked before mempool admission.

NOT YET PROVEN

Banking readiness

These code controls alone do not prove regulatory, operational, custody, liquidity or production-banking suitability.

Important: Source-level validation controls are evidence of implemented mechanisms. They are not, by themselves, evidence that the live network has sufficient miners, liquidity, uptime, decentralization, operational support or regulatory readiness for banking.

NEXT — P2P & Network Security Audit

Ab next code layer: network se transaction kaise aata hai aur node usko kaise handle karta hai.

  • Peer connection and message processing
  • Block/transaction propagation
  • Orphan transaction handling
  • Peer misbehavior and banning controls
  • DoS/rate-limit protections
  • Chain activation, fork handling and best-chain selection

Goal: identify concrete network-security mechanisms and then compare them with the Bitcoin-derived reference architecture.