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# Package elliptic

`import "crypto/elliptic"`
Overview
Index

## Overview ▾

Package elliptic implements several standard elliptic curves over prime fields.

## func GenerateKey¶

`func GenerateKey(curve Curve, rand io.Reader) (priv []byte, x, y *big.Int, err error)`

GenerateKey returns a public/private key pair. The private key is generated using the given reader, which must return random data.

## func Marshal¶

`func Marshal(curve Curve, x, y *big.Int) []byte`

Marshal converts a point into the uncompressed form specified in section 4.3.6 of ANSI X9.62.

## func Unmarshal¶

`func Unmarshal(curve Curve, data []byte) (x, y *big.Int)`

Unmarshal converts a point, serialized by Marshal, into an x, y pair. It is an error if the point is not in uncompressed form or is not on the curve. On error, x = nil.

## type Curve¶

A Curve represents a short-form Weierstrass curve with a=-3. See https://www.hyperelliptic.org/EFD/g1p/auto-shortw.html

```type Curve interface {
// Params returns the parameters for the curve.
Params() *CurveParams
// IsOnCurve reports whether the given (x,y) lies on the curve.
IsOnCurve(x, y *big.Int) bool
// Add returns the sum of (x1,y1) and (x2,y2)
Add(x1, y1, x2, y2 *big.Int) (x, y *big.Int)
// Double returns 2*(x,y)
Double(x1, y1 *big.Int) (x, y *big.Int)
// ScalarMult returns k*(Bx,By) where k is a number in big-endian form.
ScalarMult(x1, y1 *big.Int, k []byte) (x, y *big.Int)
// ScalarBaseMult returns k*G, where G is the base point of the group
// and k is an integer in big-endian form.
ScalarBaseMult(k []byte) (x, y *big.Int)
}```

### func P224¶

`func P224() Curve`

P224 returns a Curve which implements P-224 (see FIPS 186-3, section D.2.2).

The cryptographic operations are implemented using constant-time algorithms.

### func P256¶

`func P256() Curve`

P256 returns a Curve which implements NIST P-256 (FIPS 186-3, section D.2.3), also known as secp256r1 or prime256v1. The CurveParams.Name of this Curve is "P-256".

Multiple invocations of this function will return the same value, so it can be used for equality checks and switch statements.

The cryptographic operations are implemented using constant-time algorithms.

### func P384¶

`func P384() Curve`

P384 returns a Curve which implements NIST P-384 (FIPS 186-3, section D.2.4), also known as secp384r1. The CurveParams.Name of this Curve is "P-384".

Multiple invocations of this function will return the same value, so it can be used for equality checks and switch statements.

The cryptographic operations do not use constant-time algorithms.

### func P521¶

`func P521() Curve`

P521 returns a Curve which implements NIST P-521 (FIPS 186-3, section D.2.5), also known as secp521r1. The CurveParams.Name of this Curve is "P-521".

Multiple invocations of this function will return the same value, so it can be used for equality checks and switch statements.

The cryptographic operations do not use constant-time algorithms.

## type CurveParams¶

CurveParams contains the parameters of an elliptic curve and also provides a generic, non-constant time implementation of Curve.

```type CurveParams struct {
P       *big.Int // the order of the underlying field
N       *big.Int // the order of the base point
B       *big.Int // the constant of the curve equation
Gx, Gy  *big.Int // (x,y) of the base point
BitSize int      // the size of the underlying field
Name    string   // the canonical name of the curve; added in Go 1.5
}
```

`func (curve *CurveParams) Add(x1, y1, x2, y2 *big.Int) (*big.Int, *big.Int)`

### func (*CurveParams) Double¶

`func (curve *CurveParams) Double(x1, y1 *big.Int) (*big.Int, *big.Int)`

### func (*CurveParams) IsOnCurve¶

`func (curve *CurveParams) IsOnCurve(x, y *big.Int) bool`

### func (*CurveParams) Params¶

`func (curve *CurveParams) Params() *CurveParams`

### func (*CurveParams) ScalarBaseMult¶

`func (curve *CurveParams) ScalarBaseMult(k []byte) (*big.Int, *big.Int)`

### func (*CurveParams) ScalarMult¶

`func (curve *CurveParams) ScalarMult(Bx, By *big.Int, k []byte) (*big.Int, *big.Int)`