Dual Digital Signature Made Easy

Dual digital signature

hello friends welcome to part 2 of secure electronic transaction in this video we are going to discuss the concept of 12 signature in set which is a very important concept okay what do you mean by a 12 signature let's see the concept first ad well signature means a digital signature and there'll be just one single signer but there will be two receivers okay and the sender wants to send the messages which are internet for two recipients so what is the concept let us look at over here you will be having a message one there will be a message - okay which are meant for two different recipients the hash of first message is taken and MD is got we can make use of sha-1 then the hash of message - is taken you got a second MD these two are concatenated and after concatenated hash of this whole message is taken okay so this new digest is actually a hash of these two message digests which are actually generated from message 1 and message 2 then this new message digest which is a concatenation of digest 1 and digest true and actually hashed by a new head by SJ is signed by the private key so the output of this step is actually a dwell signature what is the importance of this insect we are going to discuss this in this video ok as I just discussed in the previous slide the concept of 12 signatures to link to messages which are intended for two different receivers or to different recipients in the case of secure electronic transaction we have two pieces of information that is the order information and the payment information the order information and payment information building together and the payment information truths these to the bank from the customer and the order information should reach to the merchants from the customers much and doesn't need to know about the PA similarly Bank doesn't need to know about the away it means the goal is to that only the information which one is required only he has done only that information ok so this concept of dwell signature provides a sort of extra protection to the customer so that the merchant is not at all aware about the payment information which only supposed to be known to the bank ok the link is required because we have to link together the payment information along with the order information so that one cannot one here is the merchant cannot link one order of information with the other payment information ok as I just discussed in the previous slide the merchant if the merchant can capture another order information he might tell that this particular payment information is for this particular order and not for the previous order it means every order information has to building with the payment information and the this concept simply make the two things together both the P I and Y cannot be replaced by another Y and PA this is the main concept over here ok now what actually happens in the dwell signature operation you having you means the customer over here will be having the payment information it will be having the order information when we talk about customer it means the software within the customers machines to client the hash of that is taken then P IMD that is P AMD generated hash of this one similarly ymd Katz generated these two are concatenated and hash of this is taken so that we get a pure MD this P OMD is signed or encrypted by the private key of the customer and this is the output which is known as the twelve signature this code is all about this without this explained you over here okay now this twelve signature along with some other piece of information is given by the customer to the merchant and let's see how the both verifies or both checks whether the well signature is the correct one or not okay let's see first how the well signature is verified by the merchant okay the merchant having two pieces of information because the merchant doesn't need to know the public the sorry the women information so it will be having P imd we'll see in the another video that how the merchant gets this information and how the bank gets this information okay so merchants will be having the order information mutton will be having the P imd the two pieces and function it will be having and obviously the dwell signature which the customer gives so armed with the three pieces of information y P AMD and the dual signature what happens the merchant calculates this thing it means he is having why it takes the hash of this so you'll be getting OMD then P imd and these two are concatenated and you get this value doubt this fish actually means 12 signature or just you can say it's a pure m v-not well signature now the dwell signature which was encrypted by the private key of the customer and the merchant knows the public key of the customer as well as the bank knows the public key of the customer so this 12 signature is decrypted by the public key of the customer which actually is the output P OMD and which you have got in the equation number 1 if equation number output of 1 & 2 is same then the merchant has verified that well signature okay now similarly when the bank received this information bank only need to concern the payment information he doesn't need to know the order information so Bank will be in the position of the PA ymd and the dwell signature now Bank also knows the public key of the customer so what Bank does or the software the side software within the bank system he simply calculates pu md by combining the hash of PA and the hash of OMD so you'll be getting the p o md now if you decrypt the dwell signature by the public key of the customer you will also be getting PU md and if the output of 1 + 2 is same it means bank also has verified the dwelle signature so you can see that one single message was there which was combined or you can say one single dwell signature along with some message has been given to two different parties and both have verified that yes these are the signature of the customer so if we conclude that what did we accomplish by you know this all this thing which you've just seen so we have seen that yes the merchant is see with order information has verified the signature similarly Bank has received the payment information has verified the signature and because the two things were linked together and the customer link there a and P I and yes you can prove the linkage because the ymd and P AMD were combined and signed by the private key of the customer so this finishes the concept of dwell signatures insert hope you have understood it and if you have any doubts you can ask in the query section thank you for watching this video thank you