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crypto/ted25519/ted25519/partialsig.go

@@ -0,0 +1,55 @@
+//
+// Copyright Coinbase, Inc. All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+package ted25519
+
+import "strconv"
+
+type Message []byte
+
+func (m Message) String() string {
+	return string(m)
+}
+
+const signatureLength = 64
+
+type PartialSignature struct {
+	ShareIdentifier byte   // x-coordinate of which signer produced signature
+	Sig             []byte // 64-byte signature: R || s
+}
+
+// NewPartialSignature creates a new PartialSignature
+func NewPartialSignature(identifier byte, sig []byte) *PartialSignature {
+	if l := len(sig); l != signatureLength {
+		panic("ted25519: invalid partial signature length: " + strconv.Itoa(l))
+	}
+	return &PartialSignature{ShareIdentifier: identifier, Sig: sig}
+}
+
+// R returns the R component of the signature
+func (sig *PartialSignature) R() []byte {
+	return sig.Sig[:32]
+}
+
+// S returns the s component of the signature
+func (sig *PartialSignature) S() []byte {
+	return sig.Sig[32:]
+}
+
+func (sig *PartialSignature) Bytes() []byte {
+	return sig.Sig
+}
+
+// TSign generates a signature that can later be aggregated with others to produce a signature valid
+// under the provided public key and nonce pair.
+func TSign(message Message, key *KeyShare, pub PublicKey, nonce *NonceShare, noncePub PublicKey) *PartialSignature {
+	sig := ThresholdSign(
+		reverseBytes(key.Value.Bytes()), pub,
+		message,
+		reverseBytes(nonce.Value.Bytes()), noncePub,
+	)
+	return NewPartialSignature(byte(key.ShamirShare.Identifier), sig)
+}