From e496a6536288b0b23cff6766842acc55d3a09b44 Mon Sep 17 00:00:00 2001
From: armfazh <armfazh@cloudflare.com>
Date: Fri, 4 Mar 2022 13:23:35 -0800
Subject: [PATCH 1/2] Adds Set/Copy methods for group element and scalar

---
 group/group.go        |  4 ++++
 group/ristretto255.go | 18 ++++++++++++++++++
 group/short.go        | 17 +++++++++++++++++
 3 files changed, 39 insertions(+)

diff --git a/group/group.go b/group/group.go
index 0bfaea6d9..fb56eba25 100644
--- a/group/group.go
+++ b/group/group.go
@@ -31,6 +31,8 @@ type Group interface {
 
 // Element represents an abstract element of a prime-order group.
 type Element interface {
+	Set(Element) Element
+	Copy() Element
 	IsIdentity() bool
 	IsEqual(Element) bool
 	Add(Element, Element) Element
@@ -45,6 +47,8 @@ type Element interface {
 
 // Scalar represents an integer scalar.
 type Scalar interface {
+	Set(Scalar) Scalar
+	Copy() Scalar
 	IsEqual(Scalar) bool
 	SetUint64(uint64)
 	Add(Scalar, Scalar) Scalar
diff --git a/group/ristretto255.go b/group/ristretto255.go
index 6099b53af..cbe4be00b 100644
--- a/group/ristretto255.go
+++ b/group/ristretto255.go
@@ -121,6 +121,15 @@ func (e *ristrettoElement) IsEqual(x Element) bool {
 	return e.p.Equals(&x.(*ristrettoElement).p)
 }
 
+func (e *ristrettoElement) Set(x Element) Element {
+	e.p.Set(&x.(*ristrettoElement).p)
+	return e
+}
+
+func (e *ristrettoElement) Copy() Element {
+	return &ristrettoElement{*new(r255.Point).Set(&e.p)}
+}
+
 func (e *ristrettoElement) Add(x Element, y Element) Element {
 	e.p.Add(&x.(*ristrettoElement).p, &y.(*ristrettoElement).p)
 	return e
@@ -164,6 +173,15 @@ func (s *ristrettoScalar) IsEqual(x Scalar) bool {
 	return s.s.Equals(&x.(*ristrettoScalar).s)
 }
 
+func (s *ristrettoScalar) Set(x Scalar) Scalar {
+	s.s.Set(&x.(*ristrettoScalar).s)
+	return s
+}
+
+func (s *ristrettoScalar) Copy() Scalar {
+	return &ristrettoScalar{*new(r255.Scalar).Set(&s.s)}
+}
+
 func (s *ristrettoScalar) Add(x Scalar, y Scalar) Scalar {
 	s.s.Add(&x.(*ristrettoScalar).s, &y.(*ristrettoScalar).s)
 	return s
diff --git a/group/short.go b/group/short.go
index fc25b681c..151a749e6 100644
--- a/group/short.go
+++ b/group/short.go
@@ -132,6 +132,14 @@ func (e *wElt) IsEqual(o Element) bool {
 	return e.x.Cmp(oo.x) == 0 && e.y.Cmp(oo.y) == 0
 }
 
+func (e *wElt) Set(a Element) Element {
+	aa := e.cvtElt(a)
+	e.x.Set(aa.x)
+	e.y.Set(aa.y)
+	return e
+}
+
+func (e *wElt) Copy() Element { return e.wG.zeroElement().Set(e) }
 func (e *wElt) Add(a, b Element) Element {
 	aa, bb := e.cvtElt(a), e.cvtElt(b)
 	e.x, e.y = e.c.Add(aa.x, aa.y, bb.x, bb.y)
@@ -225,6 +233,15 @@ func (s *wScl) fromBig(b *big.Int) {
 	}
 }
 
+func (s *wScl) Set(a Scalar) Scalar {
+	aa := s.cvtScl(a)
+	if err := s.UnmarshalBinary(aa.k); err != nil {
+		panic(err)
+	}
+	return s
+}
+
+func (s *wScl) Copy() Scalar { return s.wG.zeroScalar().Set(s) }
 func (s *wScl) Add(a, b Scalar) Scalar {
 	aa, bb := s.cvtScl(a), s.cvtScl(b)
 	r := new(big.Int)

From 8afee8aad0e3e1b42bd548e1e368bcbc13c2b784 Mon Sep 17 00:00:00 2001
From: armfazh <armfazh@cloudflare.com>
Date: Fri, 4 Mar 2022 13:42:34 -0800
Subject: [PATCH 2/2] Updates CopyBlinds to use group.Copy

---
 oprf/client.go | 3 +--
 oprf/oprf.go   | 8 ++++++--
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/oprf/client.go b/oprf/client.go
index 78aae0c6e..981808c0d 100644
--- a/oprf/client.go
+++ b/oprf/client.go
@@ -64,8 +64,7 @@ func (c client) blind(inputs [][]byte, blinds []Blind) (*FinalizeData, *Evaluati
 	return finData, evalReq, nil
 }
 
-func (c client) unblind(serUnblindeds [][]byte, blindeds []group.Element, blind []Blind) error {
-	var err error
+func (c client) unblind(serUnblindeds [][]byte, blindeds []group.Element, blind []Blind) (err error) {
 	invBlind := c.params.group.NewScalar()
 	U := c.params.group.NewElement()
 
diff --git a/oprf/oprf.go b/oprf/oprf.go
index 2bbbc36a3..88341f747 100644
--- a/oprf/oprf.go
+++ b/oprf/oprf.go
@@ -270,8 +270,12 @@ type FinalizeData struct {
 
 // CopyBlinds copies the serialized blinds to use when determinstically
 // invoking DeterministicBlind.
-func (d FinalizeData) CopyBlinds() []Blind {
-	return d.blinds
+func (f FinalizeData) CopyBlinds() []Blind {
+	out := make([]Blind, len(f.blinds))
+	for i, b := range f.blinds {
+		out[i] = b.Copy()
+	}
+	return out
 }
 
 // EvaluationRequest contains the blinded elements to be evaluated by the Server.