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crypto/sharing/polynomial.go

@@ -0,0 +1,35 @@
+//
+// Copyright Coinbase, Inc. All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+package sharing
+
+import (
+	"io"
+
+	"github.com/onsonr/hway/crypto/core/curves"
+)
+
+type Polynomial struct {
+	Coefficients []curves.Scalar
+}
+
+func (p *Polynomial) Init(intercept curves.Scalar, degree uint32, reader io.Reader) *Polynomial {
+	p.Coefficients = make([]curves.Scalar, degree)
+	p.Coefficients[0] = intercept.Clone()
+	for i := 1; i < int(degree); i++ {
+		p.Coefficients[i] = intercept.Random(reader)
+	}
+	return p
+}
+
+func (p Polynomial) Evaluate(x curves.Scalar) curves.Scalar {
+	degree := len(p.Coefficients) - 1
+	out := p.Coefficients[degree].Clone()
+	for i := degree - 1; i >= 0; i-- {
+		out = out.Mul(x).Add(p.Coefficients[i])
+	}
+	return out
+}