2 votes 2 votes Using the RSA public key crypto system, if p=13, q=31 and d=7, then the value of e is 101 103 105 107 Computer Networks ugcnetcse-dec2013-paper2 computer-networks network-security rsa-public-key + – go_editor asked Jul 24, 2016 • recategorized May 25, 2020 by Arjun go_editor 6.8k views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
Best answer 2 votes 2 votes Compute φ= (p − 1)(q − 1) =12 x 30 =360 choose an int e such that 1<e<φ and e & φ are co-prime d.e =1 mod φ 7. e=1 mod 360 =361 mod 360 =721 mod 360 =>7e=721 =>e=103 hence ans is B Sanjay Sharma answered Jul 24, 2016 • selected Sep 19, 2016 by Sankaranarayanan P.N Sanjay Sharma comment Share Follow See all 2 Comments See all 2 2 Comments reply Mahima Magon commented May 15, 2017 reply Follow Share Compute z=(p-1)*(q-1) i.e 12*30=360 Now, we know (de)mod z=1 so 7*103 mod 360 =1 i.e 721 mod 360 =1 So correct answer is B 0 votes 0 votes Adnan Ashraf commented May 12, 2019 reply Follow Share 7.e mode 360=1 =>(7*e)%360=1 (when 7* e will be mode with 360 reminder will be =1) =>so multiple of 360 == 7*e and reminder 1(i.e)7.e must be 361, 721, 1081, 1441, etc Dividing each of these in turn by 7 to see which is divisible by 7, we find that 721/7 = 103, hence e = 103. 1 votes 1 votes Please log in or register to add a comment.
