✘ - - - DECIPHER is a book compilation that tackles different, new and old codes/ciphers. In addition, this book begins with the definition of cryptography along with it's different terminology for begginers, and better understanding.
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‣ The Alberti Cipher is a type of polyalphabetic cipher developed by Leon Battista Alberti around 1460. It traditionally have two metal discs. One mobile, and one immobile, attached by a common axle so that the inner disc can be rotated.
The uppercase letters in the Latin alphabet is written in the outer disc, which doesn't have J, U, W, H, K or Y.
The outer disc also included the numbers 1 to 4 for use with a codebook containing preselected phrases and words with assigned four-digit values. Alberti designed his cipher technique with courtesans and diplomats in mind.
The inner disc had a randomized lowercase Latin alphabet, which doesn't have w, and j.
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How to encrypt using Alberti Cipher: ↳ Encryption uses a disk with two alphabets. By rotating a disk, it shifts an alphabet to the next letter. To encrypt, the disk is set in one position, the initial shift (which can be zero) corresponds to the number of letters shifted at the beginning.
The disk is composed of ABCDEF GHIJKLMNOPQRSTUVWXYZ for the large outer ring, and abcdefghijklmno pqrstuvwxyz for the small inner ring. C is in line with c, F is inline with f, etc. Rotating a disk by 4, then C is in line with g, and the initial shift becomes 4. Each letter of the plain text found on the outer ring, is replaced by the corresponding one (the one aligned) in the inner ring.
By default, every 4 characters (4 = period), the disk is rotated clockwise of 1 letter (1 = periodic increment), this changes the substituting alphabet.
Encryption example: ↳ Encrypt DCODE with the parameters: initial shift: 1, periodic increment: 2, period: 3.
Alphabets are such as ABCDEFGHIJKLMNOPQRSTUVWXYZ is aligned with bcdefghijklmnop qrstuvwxyza. The period begins, D is coded by e, C by d, O by p, the period (length 3) ends, the disk is rotated by 2 letters.
Alphabets are now aligned like this : ABCDEFGHIJKLMNOPQRSTUVWXYZ with defghijklmnopqrstuvwxyzabc, the new period begins, etc.
The encrypted message is edpgh.
How to decrypt using Alberti Cipher: ↳ The decryption process needs the disk (or the 2 alphabets) and the parameters: initial position, period and shift. To cipher a message, the disk is set with the corresponding initial shift. Each letter is identified on the inner disk, and is coded by the letter aligned in the outer disk.
By default, every 4 characters (4 = period), the disk is rotated counter-clockwise of 1 letter (1 = periodic increment).
Decryption Example: ↳ The parameters are: initial shift: 1, periodic increment: 2, period: 3, and the cipher message edpgh.
Alphabets are such as ABCDEFGH IJKLMNOPQRSTUVWXYZ is aligned with bcdefghijklmnopqrstuvwxyza.
The period begins, e is decoded by D, d by C, p by O, the period (length 3) ends, the disk is rotated by 2 letters.
Alphabets are now aligned like this: ABCDEFGHIJKLMNOPQRSTUVWXYZ with defghijklmnopqrstuvwxyzabc, the new period begins, etc.
