Function check_bip66 

pub fn check_bip66(
    signature: &[u8],
    height: u64,
    activation: &impl IsForkActive,
) -> Result<bool, ConsensusError>

BIP66: Strict DER Signature Validation

Enforces strict DER encoding for ECDSA signatures. Mathematical specification: Orange Paper Section 5.4.3

BIP66Check: 𝕊 × ℕ → {valid, invalid}

Activation Heights:

• Mainnet: BIP66_ACTIVATION_MAINNET (363,725)
• Testnet: Block 330,776
• Regtest: Block 0 (always active)