BLOCKCHAINS

BLOCKCHAINS

Blockchains are incredibly popular now a days.
What is a block chain how do they work what problems do they solve and how can they be used.

Like the name indicates a blockchain is a chain of blocks that contain information, this technique was originally described in 1991 by a group of researchers and was originally intended to time stamp digital documents so it’s not possible to backdate them or to tamper with them,almost like a notary.

However it went by mostly unused until it adapted by Satoshi Nakamoto in 2009 to created a digital crypto currency called bitcoin.

Now a blockchain is distributed ledger that is completely open to anyone they having interesting property, once a data has been recorded inside a blockchain it becomes very difficult to change it.

So how does that works!!!

Well take a closer look at a block. Each block contains some data, the hash of the block and the hash of the previous block.

The data that is stored inside the blocks defines the type of blockchain, the Bitcoin blockchain for example solves the details of the transactions such as the sender, the receiver and the amount of coins.
A block also has a hash, you can compare the hash to a fingerprint it identifies a block and all it’s contents and it is always unique just as a finger print.

Once the block is created it’s hash is being calculated. Changing something inside the block cause the hash to change, to another words hashes are very useful when you want to detect the changes to the block. If the fingerprint of the block changes it’s no longer the same block.

The third element inside of each block is the hash of the previous block and this effectively creates a chain of block and it’s the technique that makes the blockchain so secure.

 

Here we have a chain of three blocks and each block has an hash of the block and the hash of the previous block.
The block number three points to the block number two and the number two points to number one.
Now the first block is little bit special, it cannot points to it’s previous block, because it is the first block we call this block the Genesis block.

Now let’s say if we tamper with the second block, this causes the hash of the block to be changed as well, in turn that will make block 3 and all following blocks invalid, because they no longer store a valid hash of the previous block.
So changing a single block will make all following blocks invalid.

But using a hash is not enough to prevent tampering. Computers these days are faster and calculate hundred of thousands of hashes per second, you can effectively tamper with the block and recalculate all the hashes of other block to make the blockchain valid again.

Proof of Work

So to mitigate this blockchain has something called proof of work. it’s a mechanism that slows down the creation of a new block.

In bitcoins case it take about 10 minutes to calculate the required proof of work and add a new block to the chain, this mechanism makes it very hard to tamper with one block you need to recalculate the proof of work of all the following block.

So the security of the blockchain comes from creative use of hashing and the proof of work mechanism, but there is one more way that the block chain secured themselves and that is by being distributed. Instead of using a central entity to manage chains, blockchains use a peer to peer network and every one is allowed to join.

When someone joins this network he gets a full copy of the blockchain the node can use this to verify that everything is in order.

Now lets see what happens if some one creates a new block, that the block is sent to everyone on the network, each node then verify the blocks to make sure that the block is not tamper with and if everything checks out each node add the block to their own blockchain. All the nodes in this network creates consensus, the agree about what blocks are valid and which aren’t.

Blocks that are tampered with will be rejected by the other nodes in the network. So to successfully tamper with a blockchain, you need to tamper with all the blocks on the chain, redo the proof of work for each block and take control of more than 50% of the peer to peer network.
Only then when your tampered block becomes accepted by everyone else, so this is almost impossible to do.

 

 

Blockchains are also constantly evolving and one of the most recent development is the creation of smart contract.

The contracts are simple programs that are stored on the blockchain and it can be used to automatically exchange coins based on certain conditions.

The creation of blockchain technology peek the lot of peoples interest. Soon others realize that the technology can be used for other things likes

>> Storing medical records.
>> Creating digital notary.
>> Collecting taxes.

So now you know what a blockchain is how it works on a basic level and what problems they solve.

 

how to resize or rotate multiple images easily in linux

how to resize or rotate multiple images easily in linux

If you ever wonder how to resize or rotate multiple images in Linux, well this is the post for you,

 

Requirements

 

gtk+ 2.4.0
nautilus 2.6.0
ImageMagick
Nautilus Desktop manager

If you are using ubuntu type this command in the terminal

sudo apt-get install nautilus-image-converter

press enter key type your password

after this you need to restart your desktop manager for that type ALT + F2 in your keyboard then type “r” then press enter key this will restart your desktop manager now your newly installed extension will be loaded to the right-click menu, if not please restart your pc, see the snapshots given below

 

Office 16 Click-to-Run Extensibility Component 64-bit Registration prevents Office 365 32-bit installation Fix

Office 16 Click-to-Run Extensibility Component 64-bit Registration prevents Office 365 32-bit installation Fix

You may face this issue when you are trying to install Office 2016 after uninstalling preinstalled office 362 Demo.

To completely uninstall Office 16 Click-to-Run Extensibility Component 64-bit Registration follow the steps

  • Press Win + R to open the Command Prompt, type “installer” and click Enter to open the folder in File Explorer.
  • Add the column “Subject”, Right-click the column headers, and click More and select Subject
  • sort on the Subject column and scroll down until you locate the name “Office 16 Click-to Run Extensibility Component 64-bit Registration”
  • Right-click the MSI file and choose to uninstall

 

Now you can install Office 2016 .

Enjoy

Changing weather from Fahrenheit to Centigrade in gnome

Changing weather from Fahrenheit to Centigrade in gnome

By default gnome came with Fahrenheit as the unit for weather app , Fahrenheit was used as the official temperature scale only in the United States (including its unincorporated territories), its freely associated states in the western Pacific (Palau, the Federated States of Micronesia and the Marshall Islands), the Bahamas, Belize, and the Cayman Island. All other countries in the world now use the Celsius scale.

 

I am using Fedora and gnome as DE to change Fahrenheit to Celsius in gnome weather app you need  to open terminal then type following command line

 

gsettings set org.gnome.GWeather temperature-unit "'centigrade'"

Now open gnome weather app again, by now the temperature unit scale will be changed from Fahrenheit to Centigrade .

to change Centigrade to Fahrenheit use this command line

gsettings set org.gnome.GWeather temperature-unit "'fahrenheit'"

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Using the HP Cloud Recovery Media

Using the HP Cloud Recovery Media

If you have lost your HP recovery media which came with HP Laptop or Desktop and you need to reinstall the OS you may required to purchase the original recovery media from hp by giving a nominal fee + shipping charge , but i don’t think some of you may notice that ,by late 2016 hp release a service called “HP Cloud Recovery Media” , The HP Cloud Recovery Download Tool allows you to download recovery software to a USB drive. The recovery software works for HP PCs with Windows 10 Professional (64-bit) and Windows 7 Professional (64-bit).

What you need:

  • A blank USB drive with a minimum of 16 GB
  • An HP computer with Windows 10 Professional (64-bit) or Windows 7 Professional (64-bit)

Downloading Recovery Software:

 This software recovery solution is only for specific supported computer models with Win 7 Pro (64-bit) or Win 10 Pro (64-bit). Refer to the list of supported models to verify that your computer is supported before proceeding with this recovery solution. The speed at which the recovery software downloads depends on the quality and speed of the Internet connection.

HP Cloud Recovery Client click this link to download the client , then save and run the file , now insert your blank 16 Gb USB drive (Minimum) , read instructions carefully , clicking next will format and wipe all data from your usb drive .

Figure1: HP Cloud Recovery Download Tool Welcome screen

  • if you are downloading in a secure network then you may enter your proxy detail in the next screen , i am skipping this procedure because , i dont use any proxy , Click Next

When the Cloud Recovery tool detects the information for your device, click Next. OR

If you are downloading the recovery media on a different computer than the computer to be recovered, check the I need to enter the serial number for my HP system box to manually type in the information for the affected system.

Figure2: System Information Page

  • Use the drop-down menus to select the Recovery Options, Region, and Download Server, and then click Next.

For a better download experience, select a Download Server for your particular location.

Figure3 : Recovery Options, Region, and Download Server drop-down menus

  • Select your USB drive from the drop-down menu, and then click Next.

Figure4 : USB Preparation Page

Carefully read the confirmation message (which states that any information on the USB drive is deleted during this process), and then click OK.

Figure 5: Confirmation message

  • When the download completes, click OK.

Figure6 : Download complete

Click next .

Figure7 : Finish the download

  • To finish the download and close the program, click Finish.

The recovery download is now complete and ready for use on your HP PC with Windows 10 Professional (64-bit) or Windows 7 Professional (64-bit).

Supported Models

For a list of products that support the HP Cloud Recovery Download Tool, go to HP Cloud Recovery Supported Platforms.

Frequently Asked Questions

Review these frequently asked questions for information about using the HP Cloud Recovery Download Tool.

What should I do if an 'Invalid Serial Number' error message displays?
If an Invalid Serial Number message displays, re-enter the correct serial number.
What if a 'Model not found' error message displays?
If a Model not found error message displays, perform the following steps.
  1. Check that your device is included in the list of supported models.
  2. Re-enter the correct serial number.
I am experiencing long delays after clicking 'Next' on the welcome page of the application. What should I do?
If you experience long delays after clicking Next on the Welcome page, perform the following steps.
  1. Check your network connectivity.
  2. Restart the Cloud Recovery app and try again.
I am trying to use the recovery tool on a secure network, but it keeps failing. What should I do?

If your attempts to use the recovery tool on a secure network fail, contact the network administrator to get your proxy server, port information, and login credentials.

What if my download attempts keep failing?
If your download attempts keep failing, check for the following items.
  • Check your Internet connection.
  • Check that the system date and time are set correctly.
What if a 'Requested resource is not available' error message displays?

If you get a Requested resource is not available error message, check your network connectivity and restart the process.

What should I do if my downloads keep timing out, even after several tries?

If your downloads keep timing out, check your network connectivity. A strong Internet connection is required to complete the download.

I am getting an error message 'Disk not selectable.' What should I do?

If you get a Disk not selectable error message, make sure your USB drive has 16 GB of free space to use.

What if the process fails during the USB format?
If the download process fails during the USB formatting, check for the following items.
  1. Make sure the USB device has a minimum of 16 GB.
  2. Make sure the USB device is properly inserted into the USB port.
What should I do if the process fails when applying the file to USB?
If the download process fails when applying the file to the USB device, check for the following items.
  1. Make sure the USB device is 16 GB or more.
  2. Make sure the USB device is properly inserted into the USB port.
The USB device is not included in the list of boot devices. What should I do? (Windows 10) "Open below corresponding tab for the details"
It might be necessary to disable secure boot in the BIOS in order to start the computer using recovery media.
Use one of the following methods to open the Computer Setup Utility, and then choose your device type below for steps to disable secure boot.
  • Turn on the computer and immediately press the F10 key repeatedly, about once every second, until the Computer Setup Utility opens.
  • Turn on the computer and immediately press the Escape key repeatedly, about once every second, until the Startup menu opens. Press F10.
To navigate the Computer Setup Utility, choose menu screens by pressing the left or right arrow keys. Use the up or down arrow keys to move through the list of items on the menu screen. Press the Enter key to select an item and open a submenu. Then use the left and right arrow keys to modify the settings. Press the F10 key to save the changes and exit from a submenu, or press the Escape key to exit from a submenu without
Notebooks
Disable secure boot on notebook computers.
  1. Use the right arrow key to choose the System Configuration menu, use the down arrow key to select Boot Options, and then press Enter.
    Figure 8: System configuration

    Figure 9: Boot options

  2. Use the down arrow key to select Secure Boot, and then press Enter.
  3. Use the down arrow key to modify the setting to Disable, and then press Enter.
  4. Use the arrow keys to select Legacy Support, and then press Enter.
  5. Use the arrow keys to modify the setting to Enable, and then press Enter.
  6. Press F10 to accept the changes and exit or use the left arrow key to select the Exit, use the down arrow key to select Exit Saving Changes and then press Enter to select Yes.
  7. The Computer Setup Utility closes, and the Operating System Boot Mode Change screen displays, prompting you to confirm the Boot Options change. Type the code shown on the screen, and then press Enter to confirm the change.
    The Computer Setup Utility closes, and the computer restarts.
  8. Turn the computer off.
You can now boot from the recovery media.
Desktops
Disable secure boot on desktop computers.
  1. Use the right arrow key to choose the Security menu, use the down arrow key to select Secure Boot Configuration, and then press Enter.
    Figure 10: Security menu

  2. Press F10 when the Secure Boot Configuration window displays.
    Figure 11: Secure Boot Configuration

  3. Use the down arrow key to select Secure Boot, and then press the left or right arrow keys to modify the setting to Disable.
  4. Use the up arrow key to select Legacy Support, and then press the left or right arrow key to modify the setting to Disable.
    Figure 12: Disabling Secure Boot

  5. Press F10 to accept the changes and exit. Then press Enter or use the left arrow key to select File, use the down arrow key to select Exit Saving Changes, and then press Enter to select Yes.
  6. The Computer Setup Utility closes and the Operating System Boot Mode Change screen is displayed, prompting you to confirm the Boot Options change.
    Type the code shown on the screen, and then press Enter to confirm the changes.
    The Computer Setup Utility closes, and the computer restarts.
  7. Turn the computer off.
    You can now boot from the recovery media.
How to install Adobe flashplayer on Ubuntu

How to install Adobe flashplayer on Ubuntu

For many years adobe has abandoned its project for Linux platform , some time it gave me frustration to find a new flash player like adobe flash, eg pepper flash etc.

First you should enable Canonical Partner Repository,The Canonical Partner repository offers few proprietary apps that are free to use but not open-source.

  • open “Software & updates”
  • open “Other Software” tab
  • Check the “Canonical Parter repository”
  • Refresh your software sources when prompted , this may take some time depends on your Internet connection !

now open your terminal and type following command line to install adobe flashplayer , or you can use “ubuntu software” and just search for “adobe flash” and install it ,

sudo apt install adobe-flashplugin

Now restart your browser so that it detects your flash,

open ubuntu unity launcher and type adobe , now you can find adobe preferences. installation done  , enjoy

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