Pricing Methodology

Overview

CryptaChain uses a Volume-Weighted Average Price (VWAP) methodology to compute fair market value for crypto assets. This is the standard method accepted by most tax authorities and accounting standards (IFRS, US GAAP).

Data sources

• Prices are aggregated across multiple centralized spot markets with trust-weighted contributions
• Each source is classified as Active (contributes to VWAP) or Reserve (fallback if Active sources fail)
• Only sources with verified volume are used — sources with suspected wash trading are filtered out
• Per-source identities, the size of the source set, and per-source weights are internal methodology and are not disclosed on the public API

VWAP calculation

For each asset-currency pair on each day:

VWAP = Σ(Price_i × Volume_i × TrustMultiplier_i) / Σ(Volume_i × TrustMultiplier_i)

Where i iterates over qualifying source candles during the period and TrustMultiplier_i is the per-source weight at the historical date.

Quality controls

1. Outlier filtering — prices deviating >3 standard deviations from the running median are excluded
2. Minimum volume threshold — source-pair combinations below a minimum daily volume are excluded
3. Staleness detection — if a source hasn't reported a trade in >1 hour, it's temporarily excluded
4. Cross-validation — VWAP is cross-checked against the median price; if they diverge >5%, an alert is triggered

FX rate methodology

FX rates are sourced from the European Central Bank (ECB) via the Frankfurter API:

• Published daily at ~16:00 CET on business days
• Rates represent the reference rates (not trading rates)
• Weekend/holiday gaps filled by carrying forward the last business day rate
• 5 USD-pegged currencies use fixed rates (AED, SAR, QAR, OMR, BHD)
• BGN uses a fixed EUR peg (1.95583) per the Bulgarian currency board

Rate storage convention

All rates are stored internally as "1 foreign currency = X USD". This means:

• EUR rate of 1.0870 means 1 EUR = 1.0870 USD
• JPY rate of 0.006667 means 1 JPY = 0.006667 USD

The Frankfurter API returns rates as "1 EUR = X foreign". We invert these before storage so that all rates have a consistent base.

Update schedule

Data	Schedule
Crypto prices	Aggregated daily at 00:05 UTC
FX rates	Published ~16:00 CET Mon-Fri, imported at 18:00 CET
Pegged currencies	Constant (no update needed)
Monthly averages	Computed on 1st of each month for prior month