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hello everyone I am super Gonzaga village I work for bki in their team of c-dac spangle today I shall be demonstrating the creation and verification of digital signature using c-sharp language in Windows platform we will be using bouncy castle API for C sharp as the cryptographic library for all the cryptographic operations involved in creation and verification of digital signature for writing the c-sharp program we will be using visual Studios 15 as the IDE first I will show you how to get the bouncy castle API for C sharp and add this library in your project open the browser and just type bouncy bouncy castle API for C sharp and click the first link download the zip file from that website once you have downloaded extract the zip file at any location after extraction you can open the folder and verify the presence of bouncy castle crypto dll file now I shall show you how to create a new project using visual studios and add the bouncy castle library in your project just open visual studios click on new project and select console application give any name to your project so I have given the name as encryption/decryption and click OK once the project solution opens you can see some tabs on the right-hand side one of the tab is reference you have to add the bouncy castle crypto library using that reference tab so for adding just click add reference in your reference tab and browse where that library is situated select and add to your project once you have added the reference to your project you are ready to use that library I have already created a project with all the steps of key generation signing and verification I shall open the project and go through the code for your understanding here is my sample code for digital signing and verification if you want to check whether your crypto library is added to your project or not expand the references tab you can see the bouncy castle quick tour DLL added to your project now you need to import some namespaces in order to use the functions here you can see some of the namespaces I have already imported if by mistake you do not import any namespace the IDE is intelligent enough to prompt your port for importing the namespaces here if I scroll down in my code you can see one error is generated in RSA key pair generator which shows that you are missing a assembly reference now the IDE is giving you this show potential fixes if you click on that it will show you which all import you should do in order to remove the errors the first it is matching with my hair so if I click on this one it will automatically hold the name Spencer my project for keeper generation process I have instantiated RSA key pair generator class then initialize that object with some random value and the size of RSA key pair here I have taken the size of RSA key pair to be to 0 for 8 bit if you want to change the key size you can change here depending upon your requirement finally I am calling the generate key pair function to generate the asymmetric RSA key pair private key and public key may further be extracted as RSA key parameters to print the public key in M format I am using M writer initialize with text writer object the same line of code may be used for printing the private key as well by replacing the appropriate parameter for signing I'm using get signer function of signer utility class parameterised with sha with RSA encryption data member of pkcs object identifier this returns an object of I signer interface further I am initializing this object with the private key generated the first parameter is set to true because we want encryption of that method digest with a generated private key next I am passing the input message offset and length of the message finally I call the generate signature function to generate the digital signature in these lines of code I am converting the signature into a string for displaying at at the console I am using quite added to string function for converting of the digital signature into a string this is a user-defined function and the definition of Pi data to screen function is described over here similarly for verification of the generated digital signature I am using the same object of a China interface however initializing with public key this time for verification I am calling the verified signature function which returns a boolean status for valid and invalid state of the digital signature I am printing using a offence statement over here so this was a sample code of how to generate a digital signature and verify that signature now we learn this program to see the output of the program so first you need to build your probe solution to see whether any kind of error is there or not now run your program once I run it it is asking me to an enter any kind of a string or text after entering it is showing that key pairs are being generated and we have to wait for few minutes for generation of the key build so after generation of key pair you can see the public key it is displayed in your screen private key we are not being able to see because one should not show the private key or one should keep the private key secret with oneself next is the digital signature means the message that we have entered that is demo has been put to a hash function and the hash that is generated is encrypted with the private key to get this digital signature next in status of digital signature means after verifying of this digital signature it is showing the output that signature is that thank you