NETWORK SECURITY - DIGITAL SIGNATURE ALGORITHM (DSA)

[Music] hello friends welcome to our channel so in this today's session let us have a look on digital signature algorithm so far we have seen different algorithms that is a cryptographic algorithms which provides their security and then authentication algorithms which provides the authentication and key exchange algorithms where we have to exchange the secret key among the sender and receiver now in this session let us have a look on another bomb or security service that is digital signature algorithm so before going to the algorithm first we have to know what is the distress signal so as we move that in the symmetric encryption so we will be having a two different case one is a public key and another one is a private key where the public is available for all the users and the private key will be not shareable only it will be with a particular person right so if the message is encrypted using send a private key so this is very important so if the message or hash code or anything if the encryption is done using the sender's private key then automatically we call it as a digital signature so here the private key is not shareable so only the user or a sender can only send the message because the sender will not share their private key with any other user so the message can be encrypted only by the sender so that's why we call this process as a digital signature right so once again attributing that if the L Christian so here obviously the encryption will be done at the sender side and the decryption will be done at the receiver side so if the encryption is done by using sender's private key then automatically we can say this process as a digital signature see let us see that so consider the plaintext message English message so apply the hash functions so that we will get Ashford so this is the hash code which is appended with the plaintext message which is encrypted by using I would key obviate here you fit is game and if it is B here then the message will be in this form this is the hash board so this is the encrypted message and then we see outside it is fostered decrypted by using public key of relay which is available with all the users so that we will get again the plaintext message and hash code where again hash functions are applied so that we will get some hash board and this appended hash code will be compared so if the message has been sent like this we can say it as a discharge ignition because of the same person we are using them privately so here in this distant signature approach we have two approaches for this texture signatures what is RSA approach another one is DSS approach so this we can call it as a DSS or DAC or D is ch so DSS is a digital signature standard digital signature standard algorithm or we can simply say guess dsj that is digital signature so anything is same right so what is the RSA approach another one is a DSS approach so first let us see this RSA approach then we will move on to this DSA approach see first digital signature using RSA approach digital signature using our same approach so consider the plain text message concern the plain text message so which is applied to the hash function so that we will get a some hash hold and I apply the encryption that means that particular hash code will be encrypted by using public key of EI which is appended with this plaintext message so that we will get plaintext message and this is the encrypted hash code by using PUA so this representation is hash code which is encrypted by using public key of e so this will be sent to the receiver so receiver will receive this one again I press the hash function and sorry all right so apply the hash functions so the hash code will be generated and this one will be decrypted by losing sorry so this is digital signature we have to lose the private key of here right so it is a signal digital signature so we have to use a sender spreading so here we are using the private key of sender so here we have to decrypt it with publicly off sinner public of sender so that here as what we became and both hash codes will be compared so this is the simple approach for a digital signature for achieving the digital signature using this RSA approach here we have we are using our samples and here we have to use hash hache means sapphire don't all someone under them here in this encryption we are using RSA algorithm right so this is the encryption so here we are using the RSA algorithm and here we are using for hash functions with reference for generating this hash code we are using shall fight well or sharp one which we have already completed in the previous session right so this is the simple RSA approach next we will move to the second approach that is digital signature standard algorithm BSS approach BSS approach or we can simply say it s D si approach first consider the plain text message apply the hash function and then hash code will be generated and for this hash code input one more variable that is called K here K is not a secret key it is a random number the second number and this will be given to signature algorithm this will be given as inputs to signature algorithm and for this signatures we would use p ug that is a public key global public key along with this we will use private key of center that is PID and so that we will get the signature both signature and the plaintext will be appended so that we will get this is the plain text to conference will be resumed one is yes another one is so what are these components yes and are so here the signature elements or signature components are yes comma this is for a signature so both SNR will give that signature and then we see your side in the reverse process will be done so first hash functions will be applied and accorded with these hash functions these three also will be given to the verifying function verifying function so for this again we will use public key of global a global elements along with the global elements we will use the public key of E so that we will get the resultant and this resultant and this R will be compared so instead of writing this public key we can use it as a global public elements global public elements okay so this is the process them in our safe and when DSS approach digital signature using DSS approach so here once again let us repeat so first consider the plaintext message and then apply the hash functions again here also we have to use a shower we can do it a shot one or subtitle so we have to use this algorithm H so that we will get the hash code which is given as input to the signature is a key K is a random number which is given as a input for the signature algorithm here we will use two components here one is G g for global parameters of global companies global elements we can call unity global elements and PRA PRA is private key of user year and signature is s comma R and verification algorithm so at the center side signature algorithm will be happen and the receiver send verification algorithm will be happy so in the verification algorithm so we will use the signature companies along with the global components and here we are using the private key so here we have to use the public so here public able to use so that the resultant and the R will be compared here R is the signature major signature component so our should be compared with the resultant calculated value right so hope you understood this DSS approach so let us see the algorithm so how these will be calculated what are the formula for these calculations what is energy and what is the s and what is R and what is the V so here heat will be generated so what is a B right so let us see the furnace see now this is digital signature standard or digital signature algorithm anything so for this decision signature algorithm first we need we help to gear get the global public key components so global public key components so what are the global public key components first one is P as we go is it remember so we have to consider this prime number where P must be in between 2 power L minus 1 less than P does then realizing between 2 power L minus 1 and here L is the length of bits which is multiple of 64 next Q here Q is a prime divisor of prime divisor of P minus 1 prime divisor of P minus 1 so here we can say just I will give an example let us consider P as a level so as it is a prime number so Q must be prime divisors of n 2 minus 1 so 5 is a prime divisor of n so 5 will be the Chubais so hope you understood this right so here the Q is a prime divisor of P minus 1 next so here we're both on the friends right P Z Prime and Q is also a prime it's a prime divisor next given Jesus global component here G is a global component which is H power t minus 1 divided by Q mod P so this is the given so here P H over H isn't any integer which is not a hash code here H is any integer which lies in between 1 and P minus 1 which is any integer which lies in between 1 and P minus 1 so these all are called public key components so after considering this public key components and this public key components will be used in both the sender side and receiver side as we have seen in the previous mega right so after getting all these things now we have to select the private key of user loser private key which we call it as yet yes so X can be any random number so X can be a private key which is any random number in between 0 and Q 0 and you use the spanning next based upon the private key we have to calculate the public key so user publicly so users public key we call this Y where Y is equal to G power X naught cube so sorry G power X mod P it is it uses a be key so this is the users public so global public key conference P Q and G and then we have to select the private key of user a so which is a random number and from this random number we have to select the public sorry we have to calculate the private we have to calculate the public key so here the private key is X and public keys right so Y is calculated by losing this private key so Y is equal to G power X here G is a global public component so G of a reacts which is a private key mod p is a prime number right now so after that we have to select K okay is it a integer K is also K is also in a integer utilizing between 0 and Q it's a secret number it is a secret number next so after getting all these things we should get the signature algorithm are yes components right so next signature component so here signature component is G power K mod B mod Q right so G power mod p mod Q which is so that we have to calculate one more component that is yes yes is equal to right s is equal to K inverse K is a secret key so K inverse H off him H of M is hash functions applying all the plaintext message plus next into armed as we know DX is a private key and R is a one more signature component so mod Q so this is the signature function this is the signature function so which must be applied on the seller side now the message will be sent to the receiver now the receiver will receive and again they will apply some for functions and they will compare this signature component R with V so here is the decryption we have to so in the so the suicide we will be calculated and that V and R will be compared now verify in function verifying function so for this verifying function we will get a p-value so V is equal to G power pew 1 right where G is a public key component Y power YouTube and why is it C why is it public key mod p more cute hey G power you will wipe over you too got B mod Q now we will have to calculate is u1 and u2 so usual is it will do hash functions applied on em - W hash functions applied on em - so yeah yarn - is a message which has been received by the seller so at the sender said we will call it as young and at the receiver side whatever the message we are receiving that we call it as M - so yam - into W mod Q so u 1 is equal to a chain each of em - now these hash functions applied on the received message into W so what is that about you know so W is equal to yes - inverse mod Q what is this - so s is the signature component which is received by the receiver so s is generative at the recenter side and whatever the component received by this receiver is called s - so s - inverse mod Q will be W value and u 2 u 2 value u 2 is equal to R - into W R - W Q so this is the form so here R - is a signature component which is received at the receiver side so here M - R - yes - at the receiver side the message and signature components which are received at the deceiver and this V and this V and R so R here admins are - so V and R - will be compared so what is the comparison V is equal to is equal to R - this will become back so R - is resume comparing and V is calculated at a calculated at the Zoomer so this is calculated and the receiver side so hope you understood so once again I will repeat it so this is a digital signature algorithm so there are two approaches so one thing is if the encryption loses the private key of sender then we can say it as a digital signature that is the first thing second thing so here there are two approaches to achieve the digital signature one is our approach another one is DSS approach so coming to this is a approach previously we have seen first the hash functions will be applied on the plaintext message so that we will get the hash code and we will encrypt that particular hash code not a message only the hash code we are encrypting the hash code by using the sender's private key and appended with the plaintext message and sending to the receiver so receive receive the message and again the receiver will apply the same hash function from the plaintext message and again the hash probe will be generated and the encrypted hash code will be decrypted by using the public key of user a and both will be compared so that we that is the other sandwich coming to the second of route that is a digital signature approach here at the sender side we will use a signature algorithm and there is your sin we will use a verification so here also we will use at the center side we will use the private key and at the receiver say we will use the public key so apart from this we will use some more public key come friends like PQ and G so here P is a prime number which lies in between 2 power L minus 1 and L tutorial so here is the length of the bits which is a particular 64 next to Q is the crime division of P minus 3 minus 1 so here you have to observe it is a P minus 1 so if it is a practice of PD here P is also a prime there will be no divisor right so Q is a prime divisor of P minus 1 and G is any proper company which is used at both the sender and receiver side so all these three components will be used both in several receivers so G is a combination of both P and Q so G is equal to H over P minus 1 divided by Q mod p so if you have h is not a hash code H is in this your value which isin between 1 & 3 minus any visible right so this is also very important H is not a hash code h is in any integer h is it any integer in which i see between 1 and p minus 1 so after getting all this public key components we have to select the users private key which is a random number generator so using the random number generator we can select any I mean any number which is private key which acts as a pregnant so here then I found supplies in between 0 and Q so I have to select in this path prime private key we have to compute the public key so here the public key is Y which is equal to G properly X here G is a global key component G power X X is a public private key mod p so after completion of this we have self 1 integer secret integer yet K is not a key it is a integer this is also important right so here K is in a digit so hoots lies in between 0 and Q so let this Anderson so after getting all these things now we have to perform the signature at the sender saying and at the receiver said we have to perform this verification so the situation algorithm we will get a two-component signature components called and yes so here R is equal to G power K here G G is a global public key component power k k is an integer secret number so we can call it as a secret number so k is a secret temple mod p mod Q so we will get a value for R and yes yes is equal to K inverse is secret key universe H of M which is nothing but a hash code hash code press X is a private key and horizon one of the signature component mod Q so for this we will get a to compute sorry yes so this R and s will be sent to the resources so first these two R and s components that my signature components will be appended with the plaintext to message and then it will be sent to the receiver so immediately see here I am ready here set of side we will send em are yes if the receiver side the conference will be noted I mean the notation of these components will be changed - yum - ah - yes - so this is the receiver side this is the sender side now in the verification side that is that we are calculating at the suicide so in the verification we have to calculate the V and which is compared with the received version of our - so plea is equal to G power u 1 Y power YouTube mod P mod Q so here we have to know about u 1 and u 2 components so u 1 is calculated by using see message that means again we have to apply the hash functions on the digital message so that we will get the hash phone product with W marking here again we hope we can this w so I hope you can disagree mobile e is equal to yes one that is a resume signature component yes one hour s - s - inverse mod Q so from this we will refer you 1 and then u 2 u 2 is equal to R - R is also received signature component R - include wwe's again the signature component mark you so that you too will be tweeting so we will be calculated and this B and resealed are - will be compared so this is the digital signature algorithm digital signature what we can call it as a digital signature standard this SS or DAC so hope you understood this DSA algorithm so if you are having any doubts regarding this vs algorithm feel free to post your dogs in the comment section so that I will definitely try to clarify our your notes and if you really understood my videos like my videos and share my videos with your friends and don't forget to subscribe to our channel thanks for watching thank you very much

Channel: Sundeep Saradhi Kanthety

Views: 180,564

Keywords: sundeep, saradhi, kanthety, network security, information security, access control, authentication, authorization, confidentiality, integrity, non-repudiation, unauthorized access, security services, mechanisms, encryption, decryption, gaining access, attacks, cryptography, resources, permissions, sender, receiver, computer network, computer security, data security, dsa algorithm, dss approach, digital signature, signature, private key, public key, global key, signature components

Id: EYOmHSxSOMA

Length: 33min 0sec (1980 seconds)

Published: Fri Feb 23 2018