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package ecies
// This file contains parameters for ECIES encryption, specifying the
// symmetric encryption and HMAC parameters.
import (
"crypto"
"crypto/aes"
"crypto/cipher"
"crypto/elliptic"
"crypto/sha256"
"crypto/sha512"
"fmt"
"hash"
)
// The default curve for this package is the NIST P256 curve, which
// provides security equivalent to AES-128.
var DefaultCurve = elliptic.P256()
var (
ErrUnsupportedECDHAlgorithm = fmt.Errorf("ecies: unsupported ECDH algorithm")
ErrUnsupportedECIESParameters = fmt.Errorf("ecies: unsupported ECIES parameters")
)
type ECIESParams struct {
Hash func() hash.Hash // hash function
hashAlgo crypto.Hash
Cipher func([]byte) (cipher.Block, error) // symmetric cipher
BlockSize int // block size of symmetric cipher
KeyLen int // length of symmetric key
}
// Standard ECIES parameters:
// * ECIES using AES128 and HMAC-SHA-256-16
// * ECIES using AES256 and HMAC-SHA-256-32
// * ECIES using AES256 and HMAC-SHA-384-48
// * ECIES using AES256 and HMAC-SHA-512-64
var (
ECIES_AES128_SHA256 = &ECIESParams{
Hash: sha256.New,
hashAlgo: crypto.SHA256,
Cipher: aes.NewCipher,
BlockSize: aes.BlockSize,
KeyLen: 16,
}
ECIES_AES256_SHA256 = &ECIESParams{
Hash: sha256.New,
hashAlgo: crypto.SHA256,
Cipher: aes.NewCipher,
BlockSize: aes.BlockSize,
KeyLen: 32,
}
ECIES_AES256_SHA384 = &ECIESParams{
Hash: sha512.New384,
hashAlgo: crypto.SHA384,
Cipher: aes.NewCipher,
BlockSize: aes.BlockSize,
KeyLen: 32,
}
ECIES_AES256_SHA512 = &ECIESParams{
Hash: sha512.New,
hashAlgo: crypto.SHA512,
Cipher: aes.NewCipher,
BlockSize: aes.BlockSize,
KeyLen: 32,
}
)
var paramsFromCurve = map[elliptic.Curve]*ECIESParams{
elliptic.P256(): ECIES_AES128_SHA256,
elliptic.P384(): ECIES_AES256_SHA384,
elliptic.P521(): ECIES_AES256_SHA512,
}
func AddParamsForCurve(curve elliptic.Curve, params *ECIESParams) {
paramsFromCurve[curve] = params
}
// ParamsFromCurve selects parameters optimal for the selected elliptic curve.
// Only the curves P256, P384, and P512 are supported.
func ParamsFromCurve(curve elliptic.Curve) (params *ECIESParams) {
return paramsFromCurve[curve]
/*
switch curve {
case elliptic.P256():
return ECIES_AES128_SHA256
case elliptic.P384():
return ECIES_AES256_SHA384
case elliptic.P521():
return ECIES_AES256_SHA512
default:
return nil
}
*/
}
// ASN.1 encode the ECIES parameters relevant to the encryption operations.
func paramsToASNECIES(params *ECIESParams) (asnParams asnECIESParameters) {
if nil == params {
return
}
asnParams.KDF = asnNISTConcatenationKDF
asnParams.MAC = hmacFull
switch params.KeyLen {
case 16:
asnParams.Sym = aes128CTRinECIES
case 24:
asnParams.Sym = aes192CTRinECIES
case 32:
asnParams.Sym = aes256CTRinECIES
}
return
}
// ASN.1 encode the ECIES parameters relevant to ECDH.
func paramsToASNECDH(params *ECIESParams) (algo asnECDHAlgorithm) {
switch params.hashAlgo {
case crypto.SHA224:
algo = dhSinglePass_stdDH_sha224kdf
case crypto.SHA256:
algo = dhSinglePass_stdDH_sha256kdf
case crypto.SHA384:
algo = dhSinglePass_stdDH_sha384kdf
case crypto.SHA512:
algo = dhSinglePass_stdDH_sha512kdf
}
return
}
// ASN.1 decode the ECIES parameters relevant to the encryption stage.
func asnECIEStoParams(asnParams asnECIESParameters, params *ECIESParams) {
if !asnParams.KDF.Cmp(asnNISTConcatenationKDF) {
params = nil
return
} else if !asnParams.MAC.Cmp(hmacFull) {
params = nil
return
}
switch {
case asnParams.Sym.Cmp(aes128CTRinECIES):
params.KeyLen = 16
params.BlockSize = 16
params.Cipher = aes.NewCipher
case asnParams.Sym.Cmp(aes192CTRinECIES):
params.KeyLen = 24
params.BlockSize = 16
params.Cipher = aes.NewCipher
case asnParams.Sym.Cmp(aes256CTRinECIES):
params.KeyLen = 32
params.BlockSize = 16
params.Cipher = aes.NewCipher
default:
params = nil
}
}
// ASN.1 decode the ECIES parameters relevant to ECDH.
func asnECDHtoParams(asnParams asnECDHAlgorithm, params *ECIESParams) {
if asnParams.Cmp(dhSinglePass_stdDH_sha224kdf) {
params.hashAlgo = crypto.SHA224
params.Hash = sha256.New224
} else if asnParams.Cmp(dhSinglePass_stdDH_sha256kdf) {
params.hashAlgo = crypto.SHA256
params.Hash = sha256.New
} else if asnParams.Cmp(dhSinglePass_stdDH_sha384kdf) {
params.hashAlgo = crypto.SHA384
params.Hash = sha512.New384
} else if asnParams.Cmp(dhSinglePass_stdDH_sha512kdf) {
params.hashAlgo = crypto.SHA512
params.Hash = sha512.New
} else {
params = nil
}
}
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