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Visual cryptography is a cryptographic technique which allows visual information (pictures, text, etc.) to be encrypted in such a way that the decrypted information appears as a visual image. One of the best-known techniques has been credited to Moni Naor and Adi Shamir , who developed it in 1994. [ 1 ]
In a symmetric-key system, Bob knows Alice's encryption key. Once the message is encrypted, Alice can safely transmit it to Bob (assuming no one else knows the key). In order to read Alice's message, Bob must decrypt the ciphertext using which is known as the decryption cipher, :
Image of Bacon's cipher. Bacon's cipher or the Baconian cipher is a method of steganographic message encoding devised by Francis Bacon in 1605. [1] [2] [3] In steganograhy, a message is concealed in the presentation of text, rather than its content.
The autokey cipher, as used by members of the American Cryptogram Association, starts with a relatively-short keyword, the primer, and appends the message to it.For example, if the keyword is QUEENLY and the message is attack at dawn, then the key would be QUEENLYATTACKATDAWN.
The show's fan club, "Radio Orphan Annie's Secret Society", distributed a member's handbook that included a simple substitution cipher with a resulting numeric cipher text. This was followed the next year with a membership pin that included a cipher disk—enciphering the letters A–Z to numbers 1–26.
Decrypt the second-to-last ciphertext block using ECB mode. C n = C n || Tail (D n, B−M). Pad the ciphertext to the nearest multiple of the block size using the last B−M bits of block cipher decryption of the second-to-last ciphertext block. Swap the last two ciphertext blocks. Decrypt the (modified) ciphertext using the standard CBC mode.
The same image viewed by white, blue, green, and red lights reveals different hidden numbers. Steganography (/ ˌ s t ɛ ɡ ə ˈ n ɒ ɡ r ə f i / ⓘ STEG-ə-NOG-rə-fee) is the practice of representing information within another message or physical object, in such a manner that the presence of the concealed information would not be evident to an unsuspecting person's examination.
To decrypt, the procedure is simply reversed. Longer messages are first broken up into blocks of fixed length, called the period, and the above encryption procedure is applied to each block. One way to detect the period uses bigram statistics on ciphertext letters separated by half the period.