Calculate the private key of RSA algorithm

 Hi folks,

Today we are going to see how we can calculate the private key of RSA.

Inputs

Random prime numbers p and q

Public key (n, e)

Procedure

1. Compute n (Random modulus)

n = p * q

2. Compute e (Derived Number)

e = (p - 1) * (q - 1)

3. Form the public key

GCD(pubkey, e) should be 1

pubkey = 1 mod e

4. Private key

prikey = (1 + k * e) / pubkey

0 < k < e - Iterate until we get a number without fraction

Real example

Inputs

p = 7, q = 17, pubkey = 11

1. n = 7 * 17 = 119

2. e = (7-1) * (17-1) = 96

3. pubkey = 11 

    GCD (11, 96) = 1

4. prikey computation

k=0, (1 + 0 * 96) / 11 = 0.09

k=1, (1 + 1 * 96) / 11 = 8.81

k=2, (1 + 2 * 96) / 11 = 17.5

k=3, (1 + 3 * 96) / 11 = 26.27

k=4, (1 + 4 * 96) / 11 = 35

prikey = 35

Hoping that this blog will be useful in understanding the RSA private key computation.

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Add (append or prepend) text along with excel functions/formula in a single cell

Hi friends,

Today I have come across a situation where i want to have the cell to descriptive and to have summation of some cells. I have got information on how to do it. Please find below

Input Data:

3

4

2

I want a cell to be on top those with description and summation value

Expected output data:

Sum = 9

3

4

2

To get the output, I have written the following function

Syntax:
="Text"& function

Example:
="Sum = "& SUM(A2:A4)

We can append and prepend the text to excel function to combine text and numbers as well.

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