\n\n# eth-crypto\n\nCryptographic javascript-functions for ethereum and tutorials on how to use them together with web3js and solidity.\n\n## Tutorials\n\n- **[Creating keys and use them for ethereum transactions](./tutorials/creating-transactions.md)**\n\n In this tutorial we will create an ethereum-identity and use it to send transactions to the blockchain.\n\n- **[Sign and validate data with solidity](./tutorials/signed-data.md)**\n\n In this tutorial we will sign data in javascript and validate the signature inside of a smart-contract.\n\n- **[Sending encrypted and signed data to other identites](./tutorials/encrypted-message.md)** \n\n In this tutorial we will use the ethereum-identites and asymmetric cryptography to send an encrypted and signed message from Alice to Bob.\n\n## Sponsored by\n\n
\n\n## Using eth-crypto\n\n### Install\n\n```bash\n npm install eth-crypto --save\n```\n\n```javascript\n// es6\nimport EthCrypto from 'eth-crypto';\n\n// node\nconst EthCrypto = require('eth-crypto');\n```\n\n## API\n\n- [createIdentity()](#createidentity)\n- [publicKeyByPrivateKey()](#publickeybyprivatekey)\n- [publicKey.toAddress()](#publickeytoaddress)\n- [publicKey.compress()](#publickeycompress)\n- [publicKey.decompress()](#publickeydecompress)\n- [sign()](#sign)\n- [recover()](#recover)\n- [recoverPublicKey()](#recoverpublickey)\n- [encryptWithPublicKey()](#encryptwithpublickey)\n- [decryptWithPrivateKey()](#decryptwithprivatekey)\n- [cipher.stringify()](#cipherstringify)\n- [cipher.parse()](#cipherparse)\n- [signTransaction()](#signtransaction)\n- [txDataByCompiled()](#txdatabycompiled)\n- [calculateContractAddress()](#calculatecontractaddress)\n- [hex.compress() hex.decompress()](#hex-compressdecompress)\n### createIdentity()\n\nCreates a new ethereum-identity with privateKey, publicKey and address as hex-string.\n\n```javascript\n const identity = EthCrypto.createIdentity();\n /* > {\n address: '0x3f243FdacE01Cfd9719f7359c94BA11361f32471',\n privateKey: '0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07',\n publicKey: 'bf1cc3154424dc22191941d9f4f50b063a2b663a2337e5548abea633c1d06ece...'\n } */\n```\n\nYou can also create an identity by providing your own entropy-buffer. Use this with caution, a bad entropy can result in an unsecure private key.\n\n```javascript\n const entropy = Buffer.from('f2dacf...', 'utf-8'); // must contain at least 128 chars\n const identity = EthCrypto.createIdentity(entropy);\n /* > {\n address: '0x59c8d4d645B0a3b230DE368d815ebDE372d37Ea8',\n privateKey: '0x18cea40e44624867ddfd775b2898cdb2da29b4be92ee072b9eb02d43b6f2473a',\n publicKey: '991ce4643653ef452327ee3d1a56af19c84599d340ffd427e784...'\n } */\n```\n\n### publicKeyByPrivateKey()\n\nDerives the publicKey from a privateKey and returns it as hex-string.\n\n```javascript\n const publicKey = EthCrypto.publicKeyByPrivateKey(\n '0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07'\n );\n // > 'bf1cc3154424dc22191941d9f4f50b063a2b663a2337e5548abea633c1d06ece...'\n```\n\n### publicKey.toAddress()\n\nDerives the ethereum-address from the publicKey.\n\n```javascript\n const address = EthCrypto.publicKey.toAddress(\n 'bf1cc3154424dc22191941d9f4f50b063a2b663a2337e5548abea633c1d06ece...'\n );\n // > '0x3f243FdacE01Cfd9719f7359c94BA11361f32471'\n```\n\n### publicKey.compress()\n\nCompresses an uncompressed publicKey.\n\n```javascript\n const address = EthCrypto.publicKey.compress(\n '04a34d6aef3eb42335fb3cacb59...'\n );\n // > '03a34d6aef3eb42335fb3cacb59478c0b44c0bbeb8bb4ca427dbc7044157a5d24b' // compressed keys start with '02' or '03'\n```\n\n### publicKey.decompress()\n\nDecompresses a compressed publicKey.\n\n```javascript\n const address = EthCrypto.publicKey.decompress(\n '03a34d6aef3eb42335fb3c...'\n );\n // > 'a34d6aef3eb42335fb3cacb5947' // non-compressed keys start with '04' or no prefix\n```\n\n### sign()\n\nSigns the hash with the privateKey. Returns the signature as hex-string.\n\n```javascript\n const message = 'foobar';\n const messageHash = EthCrypto.hash.keccak256(message);\n const signature = EthCrypto.sign(\n '0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07', // privateKey\n messageHash // hash of message\n );\n // > '0xc04b809d8f33c46ff80c44ba58e866ff0d5..'\n```\n\n### recover()\n\nRecovers the signers address from the signature.\n\n```javascript\n const signer = EthCrypto.recover(\n '0xc04b809d8f33c46ff80c44ba58e866ff0d5..',\n EthCrypto.hash.keccak256('foobar') // signed message hash\n );\n // > '0x3f243FdacE01Cfd9719f7359c94BA11361f32471'\n```\n\n### recoverPublicKey()\n\nRecovers the signers `publicKey` from the signature.\n```javascript\n const signer = EthCrypto.recoverPublicKey(\n '0xc04b809d8f33c46ff80c44ba58e866ff0d5..', // signature\n EthCrypto.hash.keccak256('foobar') // message hash\n );\n // > 'bf1cc3154424dc22191941d9f4f50b063a2b663a2337e5548abea633c1d06ece..'\n```\n\n\n### encryptWithPublicKey()\n\nEncrypts the message with the publicKey so that only the corresponding privateKey can decrypt it. Returns (async) the encrypted data as object with hex-strings.\n\n```javascript\n const encrypted = await EthCrypto.encryptWithPublicKey(\n 'bf1cc3154424dc22191941d9f4f50b063a2b663a2337e5548abea633c1d06ece...', // publicKey\n 'foobar' // message\n );\n /* > {\n iv: '02aeac54cb45283b427bd1a5028552c1',\n ephemPublicKey: '044acf39ed83c304f19f41ea66615d7a6c0068d5fc48ee181f2fb1091...',\n ciphertext: '5fbbcc1a44ee19f7499dbc39cfc4ce96',\n mac: '96490b293763f49a371d3a2040a2d2cb57f246ee88958009fe3c7ef2a38264a1'\n } */\n```\n\n### decryptWithPrivateKey()\n\nDecrypts the encrypted data with the privateKey. Returns (async) the message as string.\n\n```javascript\n const message = await EthCrypto.decryptWithPrivateKey(\n '0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07', // privateKey\n {\n iv: '02aeac54cb45283b427bd1a5028552c1',\n ephemPublicKey: '044acf39ed83c304f19f41ea66615d7a6c0068d5fc48ee181f2fb1091...',\n ciphertext: '5fbbcc1a44ee19f7499dbc39cfc4ce96',\n mac: '96490b293763f49a371d3a2040a2d2cb57f246ee88958009fe3c7ef2a38264a1'\n } // encrypted-data\n );\n // 'foobar'\n```\n\n### cipher.stringify()\n\nTransforms the object with the encrypted data into a smaller string-representation.\n\n```javascript\nconst str = EthCrypto.cipher.stringify({\n iv: '02aeac54cb45283b427bd1a5028552c1',\n ephemPublicKey: '044acf39ed83c304f19f41ea66615d7a6c0068d5fc48ee181f2fb1091...',\n ciphertext: '5fbbcc1a44ee19f7499dbc39cfc4ce96',\n mac: '96490b293763f49a371d3a2040a2d2cb57f246ee88958009fe3c7ef2a38264a1'\n});\n// > '59ab06532fc965b0107977f43e69e5a4038db32099dab281c8f5aece2852...'\n```\n\n### cipher.parse()\n\nParses the string-representation back into the encrypted object.\n\n```javascript\nconst str = EthCrypto.cipher.parse('59ab06532fc965b0107977f43e69e5a4038db32099dab281c8f5aece2852...');\n/* > {\n iv: '02aeac54cb45283b427bd1a5028552c1',\n ephemPublicKey: '044acf39ed83c304f19f41ea66615d7a6c0068d5fc48ee181f2fb1091...',\n ciphertext: '5fbbcc1a44ee19f7499dbc39cfc4ce96',\n mac: '96490b293763f49a371d3a2040a2d2cb57f246ee88958009fe3c7ef2a38264a1'\n } */\n```\n\n### signTransaction()\n\nSigns a raw transaction with the privateKey. Returns a serialized tx which can be submitted to the node.\n\n```javascript\nconst identity = EthCrypto.createIdentity();\nconst rawTx = {\n from: identity.address,\n to: '0x86Fa049857E0209aa7D9e616F7eb3b3B78ECfdb0',\n value: new BN('1000000000000000000'),\n gasPrice: 5000000000,\n nonce: 0,\n gasLimit: 21000\n};\nconst signedTx = EthCrypto.signTransaction(\n rawTx,\n identity.privateKey\n);\nconsole.log(signedTx);\n// > '071d3a2040a2d2cb...'\n\n// you can now send the tx to the node\nconst receipt = await web3.eth.sendSignedTransaction(signedTx);\n```\n\n### txDataByCompiled()\n\nCreates the data-string which must be submitted with an transaction to create a contract-instance.\n\n```javascript\nconst SolidityCli = require('solidity-cli');\n\n// create compiled solidity-code\nconst compiled = await SolidityCli.compileCode(\n 'contract ExampleContract {...'\n)[':ExampleContract'];\n\nconst createCode = EthCrypto.txDataByCompiled(\n compiled.interface, // abi\n compiled.bytecode, // bytecode\n [identity.address] // constructor-arguments\n);\n\n// now you can submit this to the blockchain\nconst serializedTx = EthCrypto.signTransaction(\n {\n from: identity.address,\n nonce: 0,\n gasLimit: 5000000,\n gasPrice: 5000000000,\n data: createCode\n },\n identity.privateKey\n);\nconst receipt = await web3.eth.sendSignedTransaction(serializedTx);\n```\n\n### calculateContractAddress()\nCalculates the address for the contract from the senders address and the nonce, without deploying it to the blockchain.\n\n```javascript\n// pre-calculate address\nconst calculatedAddress = EthCrypto.calculateContractAddress(\n account.address, // address of the sender\n 3 // nonce with which the contract will be deployed\n);\n\nconst rawTx = {\n from: account.address,\n gasPrice: parseInt(gasPrice),\n nonce: 3,\n data: compiled.code\n};\nconst receipt = await state.web3.eth.sendTransaction(rawTx);\n\nconsole.log(receipt.contractAddress === calculatedAddress);\n// > true\n```\n\n### hex compress/decompress\n\n\"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. This is not a real compression, it just make your string smaller when you have to store it in utf-16 anyways.\n\n```javascript\nconst hexString = '0x107be946709e41b7895eea9f2dacf998a0a9124acbb786f0fd1a826101581a07'; // 66 chars\n\nconst utf16 = EthCrypto.hex.compress(hexString); // compress to utf16\n// > 'ၻ炞䆷襞ⶬ輦ꂩቊ쮷蛰ﴚ艡Řᨇ' // 16 chars\n\nconst base64 = EthCrypto.hex.compress(hexString, true); // compress to base64\n// > 'EHvpRnCeQbeJXuqfLaz5mKCpEkrLt4bw/RqCYQFYGgc=' // 44 chars\n\nEthCrypto.hex.decompress(utf16); // decompress from utf16\n// > '0x107be946709e41b7895eea9f2d...'\n\nEthCrypto.hex.decompress(base64, true); // decompress from base64\n// > '0x107be946709e41b7895eea9f2d...'\n\n```\n","readmeFilename":"README.md"}
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