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Incorporate low-R values into estimate signature size #2244

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May 2, 2023
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Incorporate low-R values into estimate signature size #2244

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10 changes: 10 additions & 0 deletions lightning/src/chain/keysinterface.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -85,6 +85,8 @@ pub struct DelayedPaymentOutputDescriptor {
}
impl DelayedPaymentOutputDescriptor {
/// The maximum length a well-formed witness spending one of these should have.
/// Note: If you have the grind_signatures feature enabled, this will be at least 1 byte
/// shorter.
// Calculated as 1 byte length + 73 byte signature, 1 byte empty vec push, 1 byte length plus
// redeemscript push length.
pub const MAX_WITNESS_LENGTH: usize = 1 + 73 + 1 + chan_utils::REVOKEABLE_REDEEMSCRIPT_MAX_LENGTH + 1;
Expand Down Expand Up @@ -117,6 +119,8 @@ pub struct StaticPaymentOutputDescriptor {
}
impl StaticPaymentOutputDescriptor {
/// The maximum length a well-formed witness spending one of these should have.
/// Note: If you have the grind_signatures feature enabled, this will be at least 1 byte
/// shorter.
// Calculated as 1 byte legnth + 73 byte signature, 1 byte empty vec push, 1 byte length plus
// redeemscript push length.
pub const MAX_WITNESS_LENGTH: usize = 1 + 73 + 34;
Expand Down Expand Up @@ -1188,6 +1192,8 @@ impl KeysManager {
witness: Witness::new(),
});
witness_weight += StaticPaymentOutputDescriptor::MAX_WITNESS_LENGTH;
#[cfg(feature = "grind_signatures")]
{ witness_weight -= 1; } // Guarantees a low R signature
input_value += descriptor.output.value;
if !output_set.insert(descriptor.outpoint) { return Err(()); }
},
Expand All @@ -1199,6 +1205,8 @@ impl KeysManager {
witness: Witness::new(),
});
witness_weight += DelayedPaymentOutputDescriptor::MAX_WITNESS_LENGTH;
#[cfg(feature = "grind_signatures")]
{ witness_weight -= 1; } // Guarantees a low R signature
input_value += descriptor.output.value;
if !output_set.insert(descriptor.outpoint) { return Err(()); }
},
Expand All @@ -1210,6 +1218,8 @@ impl KeysManager {
witness: Witness::new(),
});
witness_weight += 1 + 73 + 34;
#[cfg(feature = "grind_signatures")]
{ witness_weight -= 1; } // Guarantees a low R signature
input_value += output.value;
if !output_set.insert(*outpoint) { return Err(()); }
}
Expand Down