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Price Verifier

Zenex uses Pyth Lazer for price feeds. The PriceVerifierContract parses and verifies Ed25519-signed binary price updates from the Pyth Lazer network, providing cryptographically authenticated price data to the trading contract.

PriceData Structure​

Each verified price update produces one or more PriceData values:

pub struct PriceData {
    pub feed_id: u32,       // Pyth Lazer feed identifier
    pub price: i128,        // Raw price value
    pub exponent: i32,      // Decimal exponent (e.g., -8)
    pub publish_time: u64,  // Unix timestamp (seconds)
}

The price scalar used in downstream computation is derived from the exponent: price_scalar = 10^(-exponent). For the standard exponent of -8, this yields price_scalar = 100,000,000.

Verification Flow​

The contract performs a sequence of checks on every incoming price update before returning parsed data.

Verification begins with envelope parsing. The contract reads a fixed-layout binary envelope starting with magic bytes 0x821A01B9, followed by a 64-byte Ed25519 signature, a 32-byte public key, and a u16 payload length. If the magic bytes do not match, the update is rejected immediately.

The contract then performs signer verification. The public key embedded in the update must match the contract's stored trusted_signer exactly. This ensures only Pyth Lazer's authorized key can produce accepted updates.

Next, signature verification is performed via env.crypto().ed25519_verify(pubkey, payload, signature), using Soroban's host-provided cryptographic primitives. This confirms the payload has not been tampered with since signing.

With authenticity established, the contract proceeds to payload parsing. The payload begins with its own magic bytes (0x93C7D375), followed by a microsecond-precision timestamp, a channel byte, a feed count, and per-feed price/exponent/confidence properties.

Finally, a confidence check is applied when confidence data is present. If confidence * 10,000 > |price| * max_confidence_bps, the contract raises ConfidenceTooHigh. This guards against consuming prices with excessive uncertainty relative to the configured tolerance.

Access Control​

The price verifier implements OZ Ownable for access control. For standard Ownable behavior, refer to OpenZeppelin Stellar Contracts.

FunctionAuth
verify_price(update_data)Permissionless
verify_prices(update_data)Permissionless
max_confidence_bps()Permissionless
max_staleness()Permissionless
update_trusted_signer(signer)Owner only (#[only_owner])
update_max_confidence_bps(bps)Owner only
update_max_staleness(max_staleness)Owner only

Staleness Threshold​

The price verifier enforces a single configurable max_staleness parameter on all price data. Any price older than max_staleness seconds is rejected. The threshold is set at deployment and can be updated by the owner via update_max_staleness.

Prices in the future (publish_time > now) are also rejected. This prevents replay of pre-signed future prices.