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package oprf
import (
"crypto/rand"
"crypto/subtle"
"github.com/cloudflare/circl/group"
"github.com/cloudflare/circl/zk/dleq"
)
type server struct {
params
privateKey *PrivateKey
}
type Server struct{ server }
type VerifiableServer struct{ server }
type PartialObliviousServer struct{ server }
func (s server) PublicKey() *PublicKey { return s.privateKey.Public() }
func (s server) evaluate(elements []Blinded, secret Blind) []Evaluated {
evaluations := make([]Evaluated, len(elements))
for i := range elements {
evaluations[i] = s.params.group.NewElement().Mul(elements[i], secret)
}
return evaluations
}
func (s Server) Evaluate(req *EvaluationRequest) (*Evaluation, error) {
evaluations := s.server.evaluate(req.Elements, s.privateKey.k)
return &Evaluation{evaluations, nil}, nil
}
func (s VerifiableServer) Evaluate(req *EvaluationRequest) (*Evaluation, error) {
evaluations := s.server.evaluate(req.Elements, s.privateKey.k)
proof, err := dleq.Prover{Params: s.getDLEQParams()}.ProveBatch(
s.privateKey.k,
s.params.group.Generator(),
s.PublicKey().e,
req.Elements,
evaluations,
rand.Reader,
)
if err != nil {
return nil, err
}
return &Evaluation{evaluations, proof}, nil
}
func (s PartialObliviousServer) Evaluate(req *EvaluationRequest, info []byte) (*Evaluation, error) {
keyProof, evalSecret, err := s.secretFromInfo(info)
if err != nil {
return nil, err
}
evaluations := s.server.evaluate(req.Elements, evalSecret)
proof, err := dleq.Prover{Params: s.getDLEQParams()}.ProveBatch(
keyProof,
s.params.group.Generator(),
s.params.group.NewElement().MulGen(keyProof),
evaluations,
req.Elements,
rand.Reader,
)
if err != nil {
return nil, err
}
return &Evaluation{evaluations, proof}, nil
}
func (s server) secretFromInfo(info []byte) (t, tInv group.Scalar, err error) {
m, err := s.params.scalarFromInfo(info)
if err != nil {
return nil, nil, err
}
t = s.params.group.NewScalar().Add(m, s.privateKey.k)
if zero := s.params.group.NewScalar(); t.IsEqual(zero) {
return nil, nil, ErrInverseZero
}
tInv = s.params.group.NewScalar().Inv(t)
return t, tInv, nil
}
func (s server) fullEvaluate(input, info []byte) ([]byte, error) {
evalSecret := s.privateKey.k
if s.params.m == PartialObliviousMode {
var err error
_, evalSecret, err = s.secretFromInfo(info)
if err != nil {
return nil, err
}
}
element := s.params.group.HashToElement(input, s.params.getDST(hashToGroupDST))
evaluation := s.params.group.NewElement().Mul(element, evalSecret)
serEval, err := evaluation.MarshalBinaryCompress()
if err != nil {
return nil, err
}
return s.finalizeHash(s.params.hash.New(), input, info, serEval), nil
}
func (s Server) FullEvaluate(input []byte) (output []byte, err error) {
return s.fullEvaluate(input, nil)
}
func (s VerifiableServer) FullEvaluate(input []byte) (output []byte, err error) {
return s.fullEvaluate(input, nil)
}
func (s PartialObliviousServer) FullEvaluate(input, info []byte) (output []byte, err error) {
return s.fullEvaluate(input, info)
}
func (s server) verifyFinalize(input, info, expectedOutput []byte) bool {
gotOutput, err := s.fullEvaluate(input, info)
if err != nil {
return false
}
return subtle.ConstantTimeCompare(gotOutput, expectedOutput) == 1
}
func (s Server) VerifyFinalize(input, expectedOutput []byte) bool {
return s.verifyFinalize(input, nil, expectedOutput)
}
func (s VerifiableServer) VerifyFinalize(input, expectedOutput []byte) bool {
return s.verifyFinalize(input, nil, expectedOutput)
}
func (s PartialObliviousServer) VerifyFinalize(input, info, expectedOutput []byte) bool {
return s.verifyFinalize(input, info, expectedOutput)
}
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