taggedHash(tag:data:)

Computes a BIP-340 tagged hash SHA256(SHA256(tag) || SHA256(tag) || data) via secp256k1_tagged_sha256, producing a 32-byte SHA256Digest.

iOS 13.0+
macCatalyst 13.0+
macOS 10.15+
tvOS 13.0+
visionOS 1.0+
watchOS 6.0+

static func taggedHash<D>(tag: D, data: D) -> SHA256Digest where D : DataProtocol

Parameters

tag: The domain-separation tag bytes; repeated twice before data as specified by BIP-340.
data: The message bytes to hash after the two tag hashes.

Return Value

A 32-byte SHA256Digest.

Discussion

Tagged hashes prevent cross-protocol attacks by domain-separating hashes with an application-specific tag. BIP-340 uses this scheme for Schnorr signature challenges and key tweaks (e.g., tag "BIP0340/challenge").