# package dsa
`import "crypto/dsa"`
dsa包實現FIPS 186-3定義的數字簽名算法(Digital Signature Algorithm),即DSA算法。
## Index
* [Variables](#pkg-variables)
* [type ParameterSizes](#ParameterSizes)
* [type Parameters](#Parameters)
* [type PublicKey](#PublicKey)
* [type PrivateKey](#PrivateKey)
* [func GenerateParameters(params \*Parameters, rand io.Reader, sizes ParameterSizes) (err error)](#GenerateParameters)
* [func GenerateKey(priv \*PrivateKey, rand io.Reader) error](#GenerateKey)
* [func Sign(rand io.Reader, priv \*PrivateKey, hash []byte) (r, s \*big.Int, err error)](#Sign)
* [func Verify(pub \*PublicKey, hash []byte, r, s \*big.Int) bool](#Verify)
## Variables
```
var ErrInvalidPublicKey = errors.New("crypto/dsa: invalid public key")
```
非法公鑰,FIPS標準的公鑰格式是很嚴格的,但有些實現沒這么嚴格,使用這些實現的公鑰時,就會導致這個錯誤。
## type [ParameterSizes](https://github.com/golang/go/blob/master/src/crypto/dsa/dsa.go#L40 "View Source")
```
type ParameterSizes int
```
是DSA參數中的質數可以接受的字位長度的枚舉,參見FIPS 186-3 section 4.2。
```
const (
L1024N160 ParameterSizes = iota
L2048N224
L2048N256
L3072N256
)
```
## type [Parameters](https://github.com/golang/go/blob/master/src/crypto/dsa/dsa.go#L16 "View Source")
```
type Parameters struct {
P, Q, G *big.Int
}
```
Parameters代表密鑰的域參數,這些參數可以被一組密鑰共享,Q的字位長度必須是8的倍數。
## type [PublicKey](https://github.com/golang/go/blob/master/src/crypto/dsa/dsa.go#L21 "View Source")
```
type PublicKey struct {
Parameters
Y *big.Int
}
```
PublicKey代表一個DSA公鑰。
## type [PrivateKey](https://github.com/golang/go/blob/master/src/crypto/dsa/dsa.go#L27 "View Source")
```
type PrivateKey struct {
PublicKey
X *big.Int
}
```
PrivateKey代表一個DSA私鑰。
## func [GenerateKey](https://github.com/golang/go/blob/master/src/crypto/dsa/dsa.go#L151 "View Source")
## func [GenerateParameters](https://github.com/golang/go/blob/master/src/crypto/dsa/dsa.go#L55 "View Source")
```
func GenerateParameters(params *Parameters, rand io.Reader, sizes ParameterSizes) (err error)
```
GenerateParameters函數隨機設置合法的參數到params。即使機器很快,函數也可能會花費很多時間來生成參數。
```
func GenerateKey(priv *PrivateKey, rand io.Reader) error
```
GenerateKey生成一對公鑰和私鑰;priv.PublicKey.Parameters字段必須已經(被GenerateParameters函數)設置了合法的參數。
## func [Sign](https://github.com/golang/go/blob/master/src/crypto/dsa/dsa.go#L194 "View Source")
```
func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err error)
```
使用私鑰對任意長度的hash值(必須是較大信息的hash結果)進行簽名,返回簽名結果(一對大整數)。私鑰的安全性取決于密碼讀取器的熵度(隨機程度)。
注意根據FIPS 186-3 section 4.6的規定,hash必須被截斷到亞組的長度,本函數是不會自己截斷的。
## func [Verify](https://github.com/golang/go/blob/master/src/crypto/dsa/dsa.go#L249 "View Source")
```
func Verify(pub *PublicKey, hash []byte, r, s *big.Int) bool
```
使用公鑰認證hash和兩個大整數r、s構成的簽名,報告簽名是否合法。
注意根據FIPS 186-3 section 4.6的規定,hash必須被截斷到亞組的長度,本函數是不會自己截斷的。
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