Unblocking the Blockchain: Public-Key Cryptography

Updated on October 10, 2018
hengkiong profile image

Heng Kiong teaches Information Technology, including business analytics and management information systems, at a tertiary institute.

Recap From Previous Article

In the previous article, we explored how symmetric key algorithm or private-key cryptography works. We learned that there are challenges with using the same private key to encrypt and decrypt data. These are summarised below:

  1. How do we ensure that the private key is exchanged over a secure channel?
  2. An encrypted message may be stolen and decrypted by anyone who has access to the Private key.
  3. How do we trust the identify of the other party receiving the message?
  4. How do we trust that the message is from the sender, since the recipient is also having the same private key?
  5. The Sender has to keep track of multiple keys when sending multiple messages.

Public-key Cryptography

Blockchain uses Public-key cryptography which is an encryption based upon asymmetric key algorithms. Public-key cryptography uses two keys instead of one to encrypt and decrypt data.

To explain further, let's use the same example from the previous article. This time, however, A sends a lock to B instead of the private key. The lock is the public key, and known to all. Whoever wishes to send a message to A uses the lock belonging to A to secure the message. A then uses the private key to unlock the message.

Public-key Cryptography
Public-key Cryptography

Public-key Cryptography Explained Using Colours

Let us now look at public-key cryptography with the help of colours.

B uses A's public key to encrypt a message before sending to A.

Only A is able to receive this message using his own private key.

Public-key Cryptography - Encrypted with the Receiver's Public Key, Which Can Only Be Decrypted by the Receiver Using the Private Key
Public-key Cryptography - Encrypted with the Receiver's Public Key, Which Can Only Be Decrypted by the Receiver Using the Private Key

And Vice-versa ...

A wishes to send a message to B.

A uses his own private Key to encrypt the message before sending.

B uses A's public key to decrypt the message. This shows that the message originates from A, and nobody else.

Public-key Cryptography - A Message Signed With a Private Key Before Sending
Public-key Cryptography - A Message Signed With a Private Key Before Sending

Public-key cryptography clearly offers better security compared to using symmetric-key cryptography as described in the previous article.

Two different keys are used for encryption and decryption of messages for communications.

In Blockchain applications, digital signatures based upon public-key cryptography are implemented using mathematic algorithms. A pair of public and private keys are generated. Just like what you saw in the colour examples above, this pair of keys are mathematically related. So only the public key can decrypt what the private key has encrypted and vice versa. The chance that an eavesdropper (or hacker) can derive the private key from a given public key (or vice-versa) is very small.

Another article I have written explains more about mathematical formulas that can be used to implement the public-key cryptography technique used in Bitcoin and Blockchain.

For the rest of us who are not so keen on the explanation of how the public and private Keys are related mathematically, below is a diagram showing how a plaintext has been encrypted and decrypted using public-key cryptography formulae.

Public-key cryptography
Public-key cryptography

What's Next?

As mentioned earlier, digital signatures used in Blockchains are based on public-key cryptography. In Blockchain, users on the nodes need assurance that the records are non-repudiatable to avoid disputes.

We will be talking about the model of digital signature schema in the next article.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

    © 2018 Heng Kiong Yap


      0 of 8192 characters used
      Post Comment

      No comments yet.


      This website uses cookies

      As a user in the EEA, your approval is needed on a few things. To provide a better website experience, toughnickel.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

      For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://maven.io/company/pages/privacy

      Show Details
      HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
      LoginThis is necessary to sign in to the HubPages Service.
      Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
      AkismetThis is used to detect comment spam. (Privacy Policy)
      HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
      HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
      Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
      CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
      Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
      Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
      Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
      Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
      Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
      Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
      VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
      PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
      Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
      MavenThis supports the Maven widget and search functionality. (Privacy Policy)
      Google AdSenseThis is an ad network. (Privacy Policy)
      Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
      Index ExchangeThis is an ad network. (Privacy Policy)
      SovrnThis is an ad network. (Privacy Policy)
      Facebook AdsThis is an ad network. (Privacy Policy)
      Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
      AppNexusThis is an ad network. (Privacy Policy)
      OpenxThis is an ad network. (Privacy Policy)
      Rubicon ProjectThis is an ad network. (Privacy Policy)
      TripleLiftThis is an ad network. (Privacy Policy)
      Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
      Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
      Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
      Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
      ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
      Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
      ClickscoThis is a data management platform studying reader behavior (Privacy Policy)