## What is the decimation cipher?

The decimation cipher encrypts a message by using modular arithmetic. Each letter in the message is replaced by its position in the alphabet (a → 0, b → 1, …, z → 25). Multiplication is done modulo 26, and the resulting products are replaced by their corresponding letters to arrive at the encrypted message.

How do I decrypt ciphertext?

To decrypt, take the first letter of the ciphertext and the first letter of the key, and subtract their value (letters have a value equal to their position in the alphabet starting from 0). If the result is negative, add 26 (26=the number of letters in the alphabet), the result gives the rank of the plain letter.

### How do you decode a cipher?

All substitution ciphers can be cracked by using the following tips:

1. Scan through the cipher, looking for single-letter words.
2. Count how many times each symbol appears in the puzzle.
3. Pencil in your guesses over the ciphertext.
4. Look for apostrophes.
5. Look for repeating letter patterns.

Why do we use mod 26 for the affine cipher?

The function E(x)=(ax + b)MOD26 defines a valid affine cipher if a is relatively prime to 26, and b is an integer between 0 and 25, inclusive. If b = 0, then we refer to this cipher as a decimation cipher. Also note that if a = 1, then E(x)=(x + b) MOD 26 is simply a Caesar (+b) shift cipher.

#### How do I read an encrypted text message?

1. Launch TextPad and open the encrypted message in the program.
2. Select the entire text of the message by pressing the “Ctrl-A” keys.
3. Open the appropriate encryption software.
4. Enter the passphrase or password that was originally used to encrypt the message.

How do you solve Caesar cipher?

Procedure

1. Shift the entire alphabet by the number you picked and write it down below your original alphabet (as shown above).
2. Pick a message to write to your friend.
4. Give your friend the encoded message and tell them the key.

## Is vigenere cipher Monoalphabetic?

Vigenère cipher, type of substitution cipher used for data encryption in which the original plaintext structure is somewhat concealed in the ciphertext by using several different monoalphabetic substitution ciphers rather than just one; the code key specifies which particular substitution is to be employed for …

What does MOD 26 mean?

Mod 26 means you take the remainder after dividing by 26. So 36 mod 26 would give you 10. As a result, shifting by 26 is the same as not shifting by zero.

### How do you crack an affine cipher?

Since we know that each letter in plaintext is enciphered in the function of y = (ax + b) MOD m, we can break the affine cipher by solving two linear equations with two examples of x and y. Once we obtain the values of a and b, we can decipher the entire ciphertext. For example, Assume that “IF” is enciphered as “PQ”.

How do you know if he’s using secret conversations?

It’s worth noting that if you send someone a message through Secret Conversations, they will know it’s a secret chat because the message bubble, which is usually blue, will be black. Next to their image it will read ‘Encrypted from one device to the other’ to let both parties know they’re engaged in a secret chat.

#### Can encrypted messages be decrypted?

We know that if you encrypt a message with a certain public key, it can only be decrypted by the matching private key. But the opposite is also true. If you encrypt a message with a certain private key, it can only be decrypted by its matching public key.