Fax Recipient Digital Signature with airSlate SignNow

Fax recipient digital signature

hi in this video I'd like to do a relatively brief overview of how to sign and verify using the Schnoor digital signature the main advantage to the signature is that most of the computation can be done before you actually want to send a message therefore increasing speed when you actually go to send the message it's not as the time isn't as dependent on the message itself next the parameter these are all variables we're using before we can talk about how to sign a verifier a couple of things we need to understand first we have P which is a prime number we also have Q which is a factor of P minus 1 we also have to choose an a so that a to the power Q is 1 mod p these three variables here are what we call global meaning that anyone knows them these are probably posted they're just sort of a set of known variables they can potentially be used for this digital signature however the S value right here this is a secret right here the S value which is in between 0 and Q and then the V is our public key so this B value here is what we post online to allow somebody to verify our signature it is our a value to the negative s mod Q naught mod P mod Q in order to sign we have to choose a random R that is in between 0 and Q we then want to use that our to compute an x value where X is a to the R mod P we then want to comment innate with the message with X and the hash and get we get this value ie right here we also want to compute the value of y or y is r + se mod Q now I'm on pay you pump Q what we want to then send is the message Emma but we also want to send this signature which is two parts we want to send E and Y in that order and that's our signature for this message so that the receiver can verify that it was you who sent the message recall that when you were trying to sign something digitally you're not usually trying to hide the message you're just trying to verify who says they sent it actually did send it so now we've signed the message and we have sent it now the receiving parties need to be able to verify that what they've received is actually from you so just as recap what we've received is the M II and Y and what is known publicly is the a P Q and V so what we have to do to verify is first we have to compute this X prime value which equals a to the Y times me to e mod P and now what I did here is I just work the math where I copied it down here and then I substituted the V if you recall V equals a to the negative s so I substituted a to the negative s in here for V and then I rewrote that using simple exponent rules and then if you recall Y is equal to R plus s times e which I simply rearranged to solve for what I mean excuse me so for R which equals y minus s e which is what we have here and the exponent so I substituted all this and put in R so we have a to the R and if you you recall a to the R is what we said x equals so theoretically our X prime should be the original X computed by the sender if it is a true signature however we weren't given the original X to verify we can't verify that because we weren't given it so what we have to do instead is we want to check and make sure the e's are the same so we have the hash function we have the message and we have the ex-prime that we have computed right here so if we do this computation and we find that the e value that we calculate is the same as what we send we know that the whole thing winds up and it is a valid signature