Ethereum test address

1. There are two possibilities. One is that the platform didn't give you a coin, so you need to consult customer service. The second kind of wallet problem has not been reflected by you. I mentioned this situation on ZB platform before. The customer service of the platform said there was a problem with the wallet, and then returned it to me. The original account was pulled.

2.

If you want to query the transaction records on the main network, you can use Etherscan. However, if you build your own private chain, how should you query the transaction records

the answer is that you need to listen to the logs on the chain, save them in the database, and then query them in the database. For example:

< pre t = "code" L = "Java" > varaddr = & quot& quot;< br />varfilter=web3.eth.filter({fromB lock:0 ,toBlock:' latest', address:addr });< br />filter.get(function(err,transactions){
transactions.forEach(function(tx){
vartxInfo=web3.eth.getTransaction(tx.transactionHash);
/ / at this time, the transaction information txinfo can be stored in the database
})< br />});

Web3. Eth. Filter() is used to monitor the log on the chain, and Web3. Eth. Gettransaction() is used to extract the information of the specified transaction. Once the transaction information is obtained, it can be stored in the database for query

recommend a practical introction, you can see: Ethereum tutorial

3. According to the requirements of the manual, first measure whether the red and green lines correspond to the L1 of the interface; Is the yellow and black line corresponding to L2? If so, it must be the correct connection. Although the telephone line can be divided into positive and negative poles, the terminals can be connected at will, so there is a rectifier directional circuit inside the telephone. Even if the L1 and L2 lines are wrongly connected, the equipment will not be burnt out, so you can safely and boldly test.

4. This is not very clear, because the research team in the central bank's digital currency is generally the relevant personnel of the central bank departments and their think tanks. As early as 2014, domestic banking institutions began to study digital currency
at present, the central bank's research on digital currency is still at an early stage, and it only plans to launch digital currency, but it is still far away from issuing digital currency. When the central bank studies digital currency, it may study the existing mainstream digital currencies such as bitcoin, Ruitai, dogcoin, etc.

5. Ethereum is a blockchain. Compared with bitcoin, it can increase smart contracts, complete Turing and faster network speed
etherem has a lot of block chain procts with regional centralization, such as digix, gold Internet of things and so on.

6. Solid content

7. Don't change it. Now Ethereum has fallen below 180

8.

Transaction

the behavior of blockchain transaction follows different rule sets

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e to the distributed and unlicensed nature of public blockchain, anyone can sign the transaction and broadcast it to the network

according to different blockchains, traders will be charged a certain transaction fee, which depends on the needs of users rather than the value of assets in the transaction

blockchain transactions do not require any central authority verification. It only needs to use the digital signature algorithm (DSA) corresponding to its blockchain to sign it with the private key

once a transaction is signed, broadcast to the network and mined into a successful block in the network, the transaction cannot be recovered

Ethereum transaction structure

Ethereum transaction data structure: transaction 0.1 eth

{
& 39; nonce':&# 39; 0x00', // Decimal: 0
& 39; gasLimit': &# 39; 0x5208', // Decimal system: 21000
& 39; gasPrice': &# 39; 0x3b9aca00', // Decimal system: 10000000000
& 39; to': &# 39;&# 39; ，// Sending address
& 39; value': &# 39; 0x16345785d8a0000',// 100000000000000000 ，10^17
' data': &# 39; 0x', // Decimal representation of null data; chainId': 1 / / blockchain network ID
}

these data have nothing to do with the transaction content, but have something to do with the execution mode of the transaction. This is because when you send a transaction in Ethereum, you must define some other parameters to tell miners how to handle your transaction. Transaction data structure has two attribute designs & quot; gas": & quot; gasPrice",& quot; gasLimit"

" gasPrice": The unit is Gwei, which is 1 / 1000 eth, indicating the transaction cost

& quot; gasLimit": The maximum gas charge allowed for the transaction

these two values are usually filled in automatically by the wallet provider

in addition, you need to specify which Ethereum network to execute the transaction (chainid): 1 represents the Ethereum main network

ring development, tests are usually carried out locally and on the test network, and transactions are carried out through the test eth issued by the test network to avoid economic losses. After the test, enter the main network transaction

in addition, if you need to submit some other data, you can use & quot; data" And & quot; nonce" Attach as part of a transaction

a nonce (number used only once) is the value used by Ethereum to track transactions, which helps to avoid double spending and replay attacks in the network

Ethereum transaction signature

Ethereum transaction involves ECDSA algorithm. Taking JavaScript code as an example, the popular ethers.js is used to call ECDSA algorithm for transaction signature

const ethers = require(' ethers')

const signer = new ethers.Wallet(' Wallet address

signer.signTransaction({

' nonce':&# 39; 0x00', // Decimal: 0

& 39; gasLimit': &# 39; 0x5208', // Decimal: 21000

& 39; gasPrice': &# 39; 0x3b9aca00', // Decimal 10000000000

& 39; to': &# 39;&# 39; ，// Sending address

& 39; value': &# 39; 0x16345785d8a0000',// 100000000000000000 ，10^17

' data': &# 39; 0x', // Decimal representation of null data

& 39; chainId': 1 / / blockchain network ID

})

. Then (console. Log)

you can use the online application composer to deliver signed transactions to Ethereum. This is known as "offline signature.". Offline signatures are particularly useful for applications such as status channels, which are smart contracts that track the balance between two accounts and transfer funds after a signed transaction is submitted. Offline signature is also a common practice in dexes

you can also use online wallet to create signature verification and broadcast through Ethereum account

with Portis, you can sign a transaction to interact with the gas station network (GSN)

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9. How can you have an IP address unless you get it automatically,
configure by yourself command:
ifconfig
eth0
IP address
netmask
subnet mask
get IP address automatically:
dhclient

10. There are two ways to detect the hosts that are cheating ARP address in the LAN. One is to use the detection function of winarpattack to see which hosts are scanning ARP. These hosts are likely to cheat ARP address. The other is to detect which hosts' network cards in the LAN are in mixed mode, Because the network card of the host which is cheating ARP address must be set in hybrid mode, so which host's network card is in hybrid mode, it is likely to cheat ARP address

(1) using winarpattack for

this software can detect many items, and it can also detect all the attacks it can carry out through its own detection function. I have verified this on two virtual machines, The commonly used functions are as follows:

source MAC address mismatch and target MAC address mismatch
arp scanning - to detect which hosts are scanning the LAN through ARP requests, so as to get a list of hosts
arp_ Antisniff_ Scan - detect which host is in sniffer state in LAN, so as to know who is sniffing
host mainline - detect online host
host changes IP - host changes its IP address or adds a new address
host changes MAC -- host changes its MAC address
new host -- new host is found
host adds IP -- host adds a new IP address
multi IP host -- host has less than one IP address
multi MAC host -- host has less than one MAC address
attack flood -- list which hosts sent Many ARP packets to other hosts
attack spoofing -- the host sends specific ARP packets to two targets of sniff data, so the cheated data is exposed
attack deception in LAN -- the host makes all the hosts in LAN believe that it is the gateway, so the thief can sniff the data sent by all the hosts to the gateway
local ARP list changes - now winarpattacker can monitor the local ARP list. When the MAC address of a host in the local ARP list changes, winarpattacker can report this phenomenon

through winarpattack, we can roughly know which hosts in the local area are performing ARP address spoofing, but this is not the advantage of this software. We can also use more specialized software to detect, that is Antisniff<

(2) using Antisniff software for detection

this is a very classic software, but because it appeared earlier and did not update later, its best running platform is WinNT, which can also run under 95 / 98, but according to my experimental test, this software runs very unstable under 98, Under XP, it will prompt that the network card cannot be found and cannot be used. Therefore, the best platform is NT. It's really hard to find an NT installation disk these days. It took me a lot of effort to build the NT virtual machine, but the detection effect is good. It only takes three steps to get the result:

1 Define the host or network segment to be scanned

click "network configuration" - "host (s) to scan" in turn, and then select whether to scan "host" (stand-alone) or "range" (network segment range), so as to define the host to be scanned in the local area

2. Scanning

in order to speed up the scanning time, we can limit the items to be scanned, because it is to detect ARP address spoofing. In "detection tests" of "scanner configuration", just select ARP test, and then click the inverted triangle symbol to start scanning

3. View the results

if it is found that the network card of a host in the LAN is in the mixed mode, Antisniff will give an alarm immediately. First pop up a skeleton pattern, and then report which IP address of the host is in the mixed mode. Then we can check the specific results in the "report" item, Click "report on machine", and then select a specific IP host. In the ARP test res. column, if "1" appears, the network card is in mixed mode. If "0" appears, the network card is in normal mode. Why a host network card is sometimes in mixed mode and sometimes in normal mode (as shown in Figure 4), the key lies in whether the host has turned on the ARP address spoofing software at that time. From this, we can see that the detection result of Antisniff is quite accurate< Third, ARP address spoofing protection

winarpattack has its own protection function, but we actually have a better choice. I have tested it. If we install 360 security guard's ARP firewall or color shadow ARP firewall personal version and other software, the attack launched by winarpattack will not succeed, so ARP address spoofing is very annoying, However, as long as we do a good job in self-protection, we can still be immune

the purpose of introcing the above software is to let you know more about the attack content in the process of ARP address deception protection in LAN, so that you can win a hundred battles.