Priyanshu Varshney / encryption

Since things didn't work out between me and mbedtls, here are the basic encryption algorithms.

guide.txt@0:65a36a7b25d0, 2018-11-10 (annotated)

Committer:
priyanshu_varshney
Date:
Sat Nov 10 20:11:01 2018 +0000
Revision:
0:65a36a7b25d0
Simple encryption algorithms apart from mbedtls(not working)

Who changed what in which revision?

UserRevisionLine numberNew contents of line
priyanshu_varshney 0:65a36a7b25d0 1 >>>> Xor Encryption
priyanshu_varshney 0:65a36a7b25d0 2 XOR encryption (or Exclusive-OR encryption) is a common method of encrypting text into a format that cannot be trivially cracked by the average person. XOR encryption is great for storing things like game save data, and other data types that are stored locally on a users computer, that while not a big deal if they are tampered with, you would like to deter people from doing so. XOR encryption is also used often as a part of more complex encryption algorithms.
priyanshu_varshney 0:65a36a7b25d0 3
priyanshu_varshney 0:65a36a7b25d0 4 The idea behind it is that if you don't know the original character or the XOR encryption key, it is impossible to determine what either one is. However, the reason that it is not entirely secure is that data almost always contains patterns (JSON uses '{' and '}' characters, XML contains plenty of '<' and '>' characters, etc.) so if someone is able to determine the pattern and unlock even one character, they will have the key to unlocking everything else.
priyanshu_varshney 0:65a36a7b25d0 5
priyanshu_varshney 0:65a36a7b25d0 6 However secure or insecure XOR encryption really is, it has plenty of valid use cases. Any kind of deterrent added to data that you don't want users to tamper with but that they will have easy access to is a prime candidate, so long as security isn't paramount.
priyanshu_varshney 0:65a36a7b25d0 7
priyanshu_varshney 0:65a36a7b25d0 8 The concept is simple, you define a key character, and for every character in the string you want to encrypt, you apply the key. Once you want to unencrypt the encrypted data, you simply go through the string and apply the key again.
priyanshu_varshney 0:65a36a7b25d0 9
priyanshu_varshney 0:65a36a7b25d0 10 ---------------------------------------------
priyanshu_varshney 0:65a36a7b25d0 11 >>>> RSA ENCRYPTION
priyanshu_varshney 0:65a36a7b25d0 12
priyanshu_varshney 0:65a36a7b25d0 13 >> Generating Public Key :
priyanshu_varshney 0:65a36a7b25d0 14 Select two prime no's. Suppose P = 53 and Q = 59.
priyanshu_varshney 0:65a36a7b25d0 15 Now First part of the Public key : n = P*Q = 3127.
priyanshu_varshney 0:65a36a7b25d0 16
priyanshu_varshney 0:65a36a7b25d0 17 We also need a small exponent say e :
priyanshu_varshney 0:65a36a7b25d0 18 But e Must be
priyanshu_varshney 0:65a36a7b25d0 19
priyanshu_varshney 0:65a36a7b25d0 20 An integer.
priyanshu_varshney 0:65a36a7b25d0 21
priyanshu_varshney 0:65a36a7b25d0 22 Not be a factor of n.
priyanshu_varshney 0:65a36a7b25d0 23
priyanshu_varshney 0:65a36a7b25d0 24 1 < e < Φ(n) [Φ(n) is discussed below],
priyanshu_varshney 0:65a36a7b25d0 25 Let us now consider it to be equal to 3.
priyanshu_varshney 0:65a36a7b25d0 26 Our Public Key is made of n and e
priyanshu_varshney 0:65a36a7b25d0 27
priyanshu_varshney 0:65a36a7b25d0 28 >> Generating Private Key :
priyanshu_varshney 0:65a36a7b25d0 29
priyanshu_varshney 0:65a36a7b25d0 30 We need to calculate Φ(n) :
priyanshu_varshney 0:65a36a7b25d0 31 Such that Φ(n) = (P-1)(Q-1)
priyanshu_varshney 0:65a36a7b25d0 32 so, Φ(n) = 3016
priyanshu_varshney 0:65a36a7b25d0 33
priyanshu_varshney 0:65a36a7b25d0 34
priyanshu_varshney 0:65a36a7b25d0 35 Now calculate Private Key, d :
priyanshu_varshney 0:65a36a7b25d0 36 d = (k*Φ(n) + 1) / e for some integer k
priyanshu_varshney 0:65a36a7b25d0 37 For k = 2, value of d is 2011.
priyanshu_varshney 0:65a36a7b25d0 38 Now we are ready with our – Public Key ( n = 3127 and e = 3) and Private Key(d = 2011)
priyanshu_varshney 0:65a36a7b25d0 39 >> Example
priyanshu_varshney 0:65a36a7b25d0 40 Now we will encrypt “HI” :
priyanshu_varshney 0:65a36a7b25d0 41
priyanshu_varshney 0:65a36a7b25d0 42 Convert letters to numbers : H = 8 and I = 9
priyanshu_varshney 0:65a36a7b25d0 43
priyanshu_varshney 0:65a36a7b25d0 44
priyanshu_varshney 0:65a36a7b25d0 45 Thus Encrypted Data c = 89e mod n.
priyanshu_varshney 0:65a36a7b25d0 46 Thus our Encrypted Data comes out to be 1394
priyanshu_varshney 0:65a36a7b25d0 47
priyanshu_varshney 0:65a36a7b25d0 48
priyanshu_varshney 0:65a36a7b25d0 49 Now we will decrypt 1394 :
priyanshu_varshney 0:65a36a7b25d0 50
priyanshu_varshney 0:65a36a7b25d0 51 Decrypted Data = cd mod n.
priyanshu_varshney 0:65a36a7b25d0 52 Thus our Encrypted Data comes out to be 89
priyanshu_varshney 0:65a36a7b25d0 53
priyanshu_varshney 0:65a36a7b25d0 54 8 = H and I = 9 i.e. "HI".