Cryptographic javascript-functions for ethereum and how to use them together with web3 and solidity.
In this tutorial we will create an ethereum-identity and use it so send transactions to the blockchain. Creating transactions.
In this tutorial we will sign data in javascript and validate the signature inside of a smart-contract. Signed Data.
In this tutorial we will use the ethereum-identites and asymmetric cryptography to send an encrypted and signed message from alice to bob. Encrypted Message.
npm install eth-crypto --save// es6
import EthCrypto from 'eth-crypto';
// node
const EthCrypto = require('eth-crypto');- createIdentity()
- publicKeyByPrivateKey()
- addressByPublicKey()
- sign()
- recover()
- encryptWithPublicKey()
- decryptWithPrivateKey()
- signTransaction()
- txDataByCompiled()
- hex.compress() hex.decompress()
Creates a new ethereum-identity with privateKey, publicKey and address as hex-string.
const identity = EthCrypto.createIdentity();
/* > {
address: '0x3f243FdacE01Cfd9719f7359c94BA11361f32471',
privateKey: '0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07',
publicKey: 'bf1cc3154424dc22191941d9f4f50b063a2b663a2337e5548abea633c1d06ece...'
} */Derives the publicKey from a privateKey and returns it as hex-string.
const publicKey = EthCrypto.publicKeyByPrivateKey(
'0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07'
);
// > 'bf1cc3154424dc22191941d9f4f50b063a2b663a2337e5548abea633c1d06ece...'Derives the ethereum-address from the publicKey.
const address = EthCrypto.publicKeyToAddress(
'bf1cc3154424dc22191941d9f4f50b063a2b663a2337e5548abea633c1d06ece...'
);
// > '0x3f243FdacE01Cfd9719f7359c94BA11361f32471'Signs the message with the privateKey. Returns the signature as hex-string.
const signature = EthCrypto.sign(
'0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07', // privateKey
'foobar' // message
);
// > '0xc04b809d8f33c46ff80c44ba58e866ff0d5..'Recovers the signers address from the signature.
const signer = EthCrypto.recover(
'0xc04b809d8f33c46ff80c44ba58e866ff0d5..',
'foobar' // signed message
);
// > '0x3f243FdacE01Cfd9719f7359c94BA11361f32471'Encrypts the message with the publicKey so that only the corresponding privateKey can decrypt it. Returns (async) the encrypted data as object with hex-strings.
const encrypted = await EthCrypto.encryptWithPublicKey(
'bf1cc3154424dc22191941d9f4f50b063a2b663a2337e5548abea633c1d06ece...', // publicKey
'foobar' // message
);
/* > {
iv: '02aeac54cb45283b427bd1a5028552c1',
ephemPublicKey: '044acf39ed83c304f19f41ea66615d7a6c0068d5fc48ee181f2fb1091...',
ciphertext: '5fbbcc1a44ee19f7499dbc39cfc4ce96',
mac: '96490b293763f49a371d3a2040a2d2cb57f246ee88958009fe3c7ef2a38264a1'
} */Decrypts the encrypted data with the privateKey. Returns (async) the message as string.
const message = await EthCrypto.decryptWithPrivateKey(
'0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07', // privateKey
{
iv: '02aeac54cb45283b427bd1a5028552c1',
ephemPublicKey: '044acf39ed83c304f19f41ea66615d7a6c0068d5fc48ee181f2fb1091...',
ciphertext: '5fbbcc1a44ee19f7499dbc39cfc4ce96',
mac: '96490b293763f49a371d3a2040a2d2cb57f246ee88958009fe3c7ef2a38264a1'
} // encrypted-data
);
// 'foobar'Signs a raw transaction with the privateKey. Returns a serialized tx which can be submitted to the node.
const identity = EthCrypto.createIdentity();
const rawTx = {
from: identity.address,
to: '0x86Fa049857E0209aa7D9e616F7eb3b3B78ECfdb0',
value: 1000000000000000000,
gasPrice: 5000000000,
nonce: 0,
gasLimit: 21000
};
const signedTx = EthCrypto.signTransaction(
rawTx,
identity.privateKey
);
console.log(signedTx);
// > '071d3a2040a2d2cb...'
// you can now send the tx to the node
const receipt = await web3.eth.sendSignedTransaction(signedTx);Creates the data-string which must be submitted with an transaction to create a contract-instance.
const solc = require('solc');
// create compiled solidity-code
const compiled = solc.compile(
'contract ExampleContract {...',
1
).contracts[':ExampleContract'];
const createCode = EthCrypto.txDataByCompiled(
compiled.interface, // abi
compiled.bytecode, // bytecode
[identity.address] // constructor-arguments
);
// now you can submit this to the blockchain
const serializedTx = EthCrypto.signTransaction(
{
from: identity.address,
nonce: 0,
gasLimit: 5000000,
gasPrice: 5000000000,
data: createCode
},
identity.privateKey
);
const receipt = await web3.eth.sendSignedTransaction(serializedTx);Compress or decompress a hex-string to make it smaller. You can either compress to utf16 which reduces the size to about 1/4, or to base64 which reduces the size to about 4/5.
const hexString = '0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07'; // 66 chars
const utf16 = EthCrypto.hex.compress(hexString); // compress to utf16
// > 'ၻ炞䆷襞ⶬ輦ꂩቊ쮷蛰ﴚ艡Řᨇ' // 16 chars
const base64 = EthCrypto.hex.compress(hexString, true); // compress to base64
// > 'EHvpRnCeQbeJXuqfLaz5mKCpEkrLt4bw/RqCYQFYGgc=' // 44 chars
EthCrypto.hex.decompress(utf16); // decompress from utf16
// > '0x107be946709e41b7895eea9f2d...'
EthCrypto.hex.decompress(base64, true); // decompress from base64
// > '0x107be946709e41b7895eea9f2d...'