Function build_unshield_transition 

pub fn build_unshield_transition<P: OrchardProver>(
    spends: Vec<SpendableNote>,
    output_address: PlatformAddress,
    unshield_amount: u64,
    change_address: &OrchardAddress,
    fvk: &FullViewingKey,
    ask: &SpendAuthorizingKey,
    anchor: Anchor,
    prover: &P,
    memo: [u8; 36],
    fee: Option<Credits>,
    platform_version: &PlatformVersion,
) -> Result<StateTransition, ProtocolError>

Builds an Unshield state transition (shielded pool -> platform address).

Spends existing notes and sends part of the value to a transparent platform address. The shielded fee is deducted from the spent notes. Any remaining value is returned to the shielded change_address.

Parameters

• spends - Notes to spend with their Merkle paths
• output_address - Platform address to receive the unshielded funds
• unshield_amount - Amount to unshield to the platform address
• change_address - Orchard address for change output
• fvk - Full viewing key for spend authorization
• ask - Spend authorizing key for RedPallas signatures
• anchor - Sinsemilla root of the note commitment tree (Orchard Anchor)
• prover - Orchard prover (holds the Halo 2 proving key)
• memo - 36-byte structured memo for the change output (4-byte type tag + 32-byte payload)
• fee - Optional fee override; if None, the minimum fee is computed automatically. If Some, must be >= the minimum fee.
• platform_version - Protocol version