– Jul 18 '12 at 18:11. You are missing a key point - public and private keys are separate, and you cannot calculate one based on the other. That is kind of the point of public key encryption. Issues with using raw RSA aside, if you have something encrypted with the public key, you need to have the corresponding private key to decrypt it. Asymmetric Part 2 - RSA includes tutorial on how to encrypt and decrypt as well as calculating the keys and euclidean algorithm. An RSA private key, meanwhile, requires at a minimum the following two values patidarayush11 / RSA-Calculator Star 15 Code Issues Pull requests RSA is the algorithm used by modern computers to encrypt and decrypt messages.
Encryption uses a classic alphabet, and two integers, called coefficients or keys A and B, these are the parameters of the affine function Ax+B.
Example: Encrypt DCODE with the keys A=5, B=3 and the English/latin alphabet ABCDEFGHIJKLMNOPQRSTUVWXYZ.
For each letter of the alphabet is associated to the value of its position in the alphabet (starting at 0).
Example: By default, A=0, B=1,..., Z=25, but it is possible (but not recommended) to use A=1, ..., Y=25, Z=0 using the alphabet ZABCDEFGHIJKLMNOPQRSTUVWXY.
For each letter of value $ x $ of the plain text, is associated a value $ y $, resulting of the affine function $ y = A times x + B mod 26 $ (with $ 26 $ the alphabet size). For each value $ y $, corresponds a letter with the same position in the alphabet, it is the ciphered letter. The Affine ciphertext is the replacement of all the letters by the new ones.
Example:
DCODE
is crypted What Is A Decryption Key
SNVSXRsa Decryption Key Calculator Free
| Plain letter | $ x $ | $ y $ | Cipher letter |
| D | 3 | $ 5 times 3 + 3 = 18 $ | S |
| O | 14 | $ 5 times 14 + 3 = 73 = 21 mod 26 $ | V |