elgamal

Documentation

Overview

Package elgamal is an ElGamal implementation based on the DeDiS framework, suitable for usage with any group in which the Decisional Diffie-Hellman problem (DDH) is hard. Only supports encryption of group elements, not of arbitrary byte arrays.

Index

• func GenerateKeyPair(suite abstract.Suite) (*PriKey, *PubKey)
• func Unpack(ciphers []*CipherText) ([]abstract.Point, []abstract.Point)
• type CipherText
  • func Add(left *CipherText, right *CipherText, pk *PubKey) *CipherText
  • func Pack(c1 []abstract.Point, c2 []abstract.Point) []*CipherText
  • func (c *CipherText) Randomize(pk *PubKey) *CipherText
• type PriKey
  • func (sk *PriKey) Decrypt(ciphertext *CipherText) abstract.Point
  • func (sk *PriKey) PartialDecrypt(ciphertext *CipherText) *CipherText
  • func (sk *PriKey) PartialProofDecrypt(ciphertext *CipherText, nonce string) (*CipherText, []byte, error)
  • func (sk *PriKey) ProofDecrypt(ciphertext *CipherText, nonce string) (abstract.Point, []byte, error)
• type PubKey
  • func SumKeys(keys []*PubKey) *PubKey
  • func (pk *PubKey) Encrypt(plaintext abstract.Point) *CipherText
  • func (pk *PubKey) VerifyProof(ciphertext *CipherText, plaintext abstract.Point, prf []byte, nonce string) error

Functions

func GenerateKeyPair

func GenerateKeyPair(suite abstract.Suite) (*PriKey, *PubKey)

GenerateKeyPair generates a new random private/public keypair in the specified group

func Unpack

func Unpack(ciphers []*CipherText) ([]abstract.Point, []abstract.Point)

Unpack an array of ciphertexts to their separate points

Types

type CipherText

type CipherText struct {
	C1 abstract.Point
	C2 abstract.Point
}

CipherText is an ElGamal ciphertext

func Add

func Add(left *CipherText, right *CipherText, pk *PubKey) *CipherText

Add to ciphertexts, resulting in a new ciphertext whose plaintext is the sum of the plaintexts of the two arguments.

func Pack

func Pack(c1 []abstract.Point, c2 []abstract.Point) []*CipherText

Pack two arrays of points to an array of ciphertexts

func (*CipherText) Randomize

func (c *CipherText) Randomize(pk *PubKey) *CipherText

Randomize modifies the ciphertext into a new ciphertext of the same ciphertext (by multiplying it with an ecryption of 1 under the same public key).

type PriKey

type PriKey struct {
	PubKey
	Secret abstract.Secret
}

PriKey is an ElGamal private key

func (*PriKey) Decrypt

func (sk *PriKey) Decrypt(ciphertext *CipherText) abstract.Point

Decrypt the specified ciphertext, resulting in a plaintext point.

func (*PriKey) PartialDecrypt

func (sk *PriKey) PartialDecrypt(ciphertext *CipherText) *CipherText

PartialDecrypt performs the decryption operation on c2 normally, but keep c1

func (*PriKey) PartialProofDecrypt

func (sk *PriKey) PartialProofDecrypt(ciphertext *CipherText, nonce string) (*CipherText, []byte, error)

PartialProofDecrypt does the same as ProofDecrypt, but keeps c1

func (*PriKey) ProofDecrypt

func (sk *PriKey) ProofDecrypt(ciphertext *CipherText, nonce string) (abstract.Point, []byte, error)

ProofDecrypt decrypts the specified ciphertext, and include a proof that we did this correctly (i.e., that the ciphertext was indeed an encryption of the plaintext).

type PubKey

type PubKey struct {
	Suite abstract.Suite
	Base  abstract.Point
	Key   abstract.Point
}

PubKey is an ElGamal public key

func SumKeys

func SumKeys(keys []*PubKey) *PubKey

SumKeys sums the given public keys (more specifically, their h's)

func (*PubKey) Encrypt

func (pk *PubKey) Encrypt(plaintext abstract.Point) *CipherText

Encrypt the specified element with respect to the public key

func (*PubKey) VerifyProof

func (pk *PubKey) VerifyProof(ciphertext *CipherText, plaintext abstract.Point, prf []byte, nonce string) error

VerifyProof verifies a decryption proof against a given public key, cipher text and plaintext

• that is, check if the proof indeed shows that the ciphertext was an encryption to the public key of the plaintext.