ECKey utils

Elliptic curve signature, public and private key generation and public key verification are realized.
Signature algorithm ECDSA

``bash
npm i eckey-util --save
`

#### Create private key
`js
const ECKey = require('eckey-util')
ECKey.createPrivate()
`

#### Get public key
`js
ECKey.getPublicKey(privateKey)
`

#### Sign
`js
let signed = ECKey.sign('Hello world!', privateKey)
`
#### SignHash
`js
let signed = ECKey.signHash(ECKey.createHash('Hello world!'), privateKey)
`

#### Verify
`js
ECKey.verify('Hello world!', signed, publicKey)
`

#### VerifyHash
`js
ECKey.verifyHash(ECKey.createHash('Hello world!'), Buffer.from(signed, 'hex'), publicKey)
``