The first recorded uses of steganography can be traced back to 440 BC in Greece, when Herodotus mentions two examples in his Histories. History A chart from Johannes Trithemius's Steganographia copied by Dr John Dee in 1591 The change is so subtle that someone who is not specifically looking for it is unlikely to notice the change. For example, a sender might start with an innocuous image file and adjust the color of every hundredth pixel to correspond to a letter in the alphabet. Media files are ideal for steganographic transmission because of their large size. In digital steganography, electronic communications may include steganographic coding inside of a transport layer, such as a document file, image file, program, or protocol. Steganography includes the concealment of information within computer files. Whereas cryptography is the practice of protecting the contents of a message alone, steganography is concerned with concealing both the fact that a secret message is being sent and its contents. Plainly visible encrypted messages, no matter how unbreakable they are, arouse interest and may in themselves be incriminating in countries in which encryption is illegal. The advantage of steganography over cryptography alone is that the intended secret message does not attract attention to itself as an object of scrutiny. Some implementations of steganography that lack a formal shared secret are forms of security through obscurity, while key-dependent steganographic schemes try to adhere to Kerckhoffs's principle. For example, the hidden message may be in invisible ink between the visible lines of a private letter. Generally, the hidden messages appear to be (or to be part of) something else: images, articles, shopping lists, or some other cover text. The first recorded use of the term was in 1499 by Johannes Trithemius in his Steganographia, a treatise on cryptography and steganography, disguised as a book on magic. The word steganography comes from Greek steganographia, which combines the words steganós ( στεγανός), meaning "covered or concealed", and -graphia ( γραφή) meaning "writing". In computing/electronic contexts, a computer file, message, image, or video is concealed within another file, message, image, or video. Steganography ( / ˌ s t ɛ ɡ ə ˈ n ɒ ɡ r ə f i/ ( listen) 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 information is not evident to human inspection. The same image viewed by white, blue, green, and red lights reveals different hidden numbers. For the prefix "Stego-" as used in taxonomy, see List of commonly used taxonomic affixes. Sources: & Image source: and it is in public domain.For the process of writing in shorthand, see Stenography. Because these drawings and notes were never published, this functioning of the valve remained unknown until 1968, when two Oxford engineers published a paper in Nature describing this mechanism, with their only reference being da Vinci’s illustrations and notes of the heart. He observed vortices at the root of the aorta and correctly hypothesized that the vortices helped close the aortic valve. He utilized a self-constructed glass model of a bovine heart filled with grass seeds suspended in water. Most impressive were his observations of the aortic valve. He also described the mechanics of blood flow through the chambers, with the atria contracting together and the ventricles relaxing together, and vice versa. Da Vinci was the first to describe the heart as a muscle and a four-chambered organ. He was particularly fascinated by the heart and the flow of blood. As an architect-engineer, Leonardo da Vinci was interested in the relationship between mechanics and human anatomy.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |