oprf

Documentation

Overview

Package oprf provides an Oblivious Pseudo-Random Function protocol.

An Oblivious Pseudorandom Function (OPRFs) is a two-party protocol for computing the output of a PRF. One party (the server) holds the PRF secret key, and the other (the client) holds the PRF input.

Obliviousness: Ensures that the server does not learn anything about the client's input during the Evaluation step.

Verifiability: Allows the client to verify that the server used a committed secret key during Evaluation step.

OPRF is defined on draft-irtf-cfrg-voprf: https://datatracker.ietf.org/doc/draft-irtf-cfrg-voprf

Index

• Variables
• func GetSizes(id SuiteID) (s struct{ ... }, err error)
• type Blind
• type Blinded
• type Client
  • func NewClient(id SuiteID) (*Client, error)
  • func NewVerifiableClient(id SuiteID, pkS *PublicKey) (*Client, error)
  • func (c *Client) Finalize(r *ClientRequest, e *Evaluation, info []byte) ([][]byte, error)
  • func (s *Client) GetMode() Mode
  • func (c *Client) Request(inputs [][]byte) (*ClientRequest, error)
• type ClientRequest
  • func (r ClientRequest) BlindedElements() [][]byte
• type Evaluation
• type Mode
• type PrivateKey
  • func DeriveKey(id SuiteID, mode Mode, seed []byte) (*PrivateKey, error)
  • func GenerateKey(id SuiteID, rnd io.Reader) (*PrivateKey, error)
  • func (k *PrivateKey) Deserialize(id SuiteID, data []byte) error
  • func (k *PrivateKey) Public() *PublicKey
  • func (k *PrivateKey) Serialize() ([]byte, error)
• type Proof
• type PublicKey
  • func (k *PublicKey) Deserialize(id SuiteID, data []byte) error
  • func (k *PublicKey) Serialize() ([]byte, error)
• type SerializedElement
• type SerializedScalar
• type Server
  • func NewServer(id SuiteID, skS *PrivateKey) (*Server, error)
  • func NewVerifiableServer(id SuiteID, skS *PrivateKey) (*Server, error)
  • func (s *Server) Evaluate(blindedElements []Blinded, info []byte) (*Evaluation, error)
  • func (s *Server) FullEvaluate(input, info []byte) ([]byte, error)
  • func (s *Server) GetMode() Mode
  • func (s *Server) GetPublicKey() *PublicKey
  • func (s *Server) VerifyFinalize(input, info, expectedOutput []byte) bool
• type SuiteID
• type UnBlinded

Variables

var ErrUnsupportedSuite = errors.New("non-supported suite")

ErrUnsupportedSuite is thrown when requesting a non-supported suite.

Functions

func GetSizes

func GetSizes(id SuiteID) (
	s struct {
		SerializedElementLength uint // Size in bytes of a serialized element.
		SerializedScalarLength  uint // Size in bytes of a serialized scalar.
		OutputLength            uint // Size in bytes of OPRF's output.
	},
	err error,
)

GetSizes returns the size in bytes of a SerializedElement, SerializedScalar, and the length of the OPRF's output protocol.

Types

type Blind

type Blind group.Scalar

type Blinded

type Blinded = SerializedElement

type Client

type Client struct {
	// contains filtered or unexported fields
}

Client is a representation of a OPRF client during protocol execution.

func NewClient

func NewClient(id SuiteID) (*Client, error)

NewClient creates a client in base mode.

func NewVerifiableClient

func NewVerifiableClient(id SuiteID, pkS *PublicKey) (*Client, error)

NewVerifiableClient creates a client in verifiable mode. A server's public key must be provided.

func (*Client) Finalize

func (c *Client) Finalize(r *ClientRequest, e *Evaluation, info []byte) ([][]byte, error)

Finalize computes the signed token from the server Evaluation and returns the output of the OPRF protocol. The function uses server's public key to verify the proof in verifiable mode.

func (*Client) GetMode

func (s *Client) GetMode() Mode

func (*Client) Request

func (c *Client) Request(inputs [][]byte) (*ClientRequest, error)

Request generates a request for server passing an array of inputs to be evaluated by server.

type ClientRequest

type ClientRequest struct {
	// contains filtered or unexported fields
}

ClientRequest is a structure to encapsulate the output of a Request call.

func (ClientRequest) BlindedElements

func (r ClientRequest) BlindedElements() [][]byte

BlindedElements returns the serialized blinded elements produced for the client request.

type Evaluation

type Evaluation struct {
	Elements []SerializedElement
	Proof    *Proof
}

type Mode

type Mode = uint8

Mode specifies properties of the OPRF protocol.

const (
	// BaseMode provides obliviousness.
	BaseMode Mode = 0x00
	// VerifiableMode provides obliviousness and verifiability.
	VerifiableMode Mode = 0x01
)

type PrivateKey

type PrivateKey struct {
	// contains filtered or unexported fields
}

func DeriveKey

func DeriveKey(id SuiteID, mode Mode, seed []byte) (*PrivateKey, error)

DeriveKey derives a pair of keys given a seed and in accordance with the suite and mode.

func GenerateKey

func GenerateKey(id SuiteID, rnd io.Reader) (*PrivateKey, error)

GenerateKey generates a pair of keys in accordance with the suite. Panics if rnd is nil.

func (*PrivateKey) Deserialize

func (k *PrivateKey) Deserialize(id SuiteID, data []byte) error

func (*PrivateKey) Public

func (k *PrivateKey) Public() *PublicKey

func (*PrivateKey) Serialize

func (k *PrivateKey) Serialize() ([]byte, error)

type Proof

type Proof struct {
	C, S SerializedScalar
}

type PublicKey

type PublicKey struct {
	// contains filtered or unexported fields
}

func (*PublicKey) Deserialize

func (k *PublicKey) Deserialize(id SuiteID, data []byte) error

func (*PublicKey) Serialize

func (k *PublicKey) Serialize() ([]byte, error)

type SerializedElement

type SerializedElement = []byte

type SerializedScalar

type SerializedScalar = []byte

type Server

type Server struct {
	// contains filtered or unexported fields
}

Server is a representation of a OPRF server during protocol execution.

func NewServer

func NewServer(id SuiteID, skS *PrivateKey) (*Server, error)

NewServer creates a Server in base mode, and generates a key if no skS is provided.

func NewVerifiableServer

func NewVerifiableServer(id SuiteID, skS *PrivateKey) (*Server, error)

NewVerifiableServer creates a Server in verifiable mode, and generates a key if no skS is provided.

func (*Server) Evaluate

func (s *Server) Evaluate(blindedElements []Blinded, info []byte) (*Evaluation, error)

Evaluate evaluates a set of blinded inputs from the client.

func (*Server) FullEvaluate

func (s *Server) FullEvaluate(input, info []byte) ([]byte, error)

FullEvaluate performs a full OPRF protocol at server-side.

func (*Server) GetMode

func (s *Server) GetMode() Mode

func (*Server) GetPublicKey

func (s *Server) GetPublicKey() *PublicKey

GetPublicKey returns the public key corresponding to the server.

func (*Server) VerifyFinalize

func (s *Server) VerifyFinalize(input, info, expectedOutput []byte) bool

VerifyFinalize performs a full OPRF protocol and returns true if the output matches the expected output.

type SuiteID

type SuiteID = uint16

SuiteID identifies supported suites.

const (
	// OPRFP256 represents the OPRF with P-256 and SHA-256.
	OPRFP256 SuiteID = 0x0003
	// OPRFP384 represents the OPRF with P-384 and SHA-512.
	OPRFP384 SuiteID = 0x0004
	// OPRFP521 represents the OPRF with P-521 and SHA-512.
	OPRFP521 SuiteID = 0x0005
)

type UnBlinded

type UnBlinded = SerializedElement