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What is a QR Code?
A QR code is a mangled looking barcode type of square graphic that you can scan using your phone or other mobile devices. Typically you need some kind of custom app on your iphone or android device and this software will act as a scanner and be able to read the black and white pixel blocks that make up a QR code.
Usually a QR code will contain a website URL and scanning the code will take you to a business website or some special video presentation created for the QR campaign. QR codes are becoming very popular as part of outdoor advertising such as on billboards or as part of ads on public transit. Any place where people are on the go with their mobile devices or cell phones is a prime creative place for QR code ads. Read More
A wireless network with WPA-PSK encryption requires a passphrase (the pre-shared key) to be entered to get access to the network. Most wireless drivers accept the passphrase as a string of at most 63 characters, and internally convert the passphrase to a 256-bit key. However, some software also allows the key to be entered directly in the form of 64 hexadecimal digits. It is therefore occasionally useful to be able to calculate the 64-digit hexadecimal key that corresponds to a given passphrase.
ASCII is an encoding system, known as an abbreviation for the American Standard Code for Information Interchange. Designed initially for old type computers and printers from telegraphic codes, it was based on 128 symbols including 10 numbers, 26 letters of English alphabet, a number of punctuation marks, etc. The system represents visible characters or commands for printing like "start", "wait", "complete", etc. The latest versions of ASCII systems are very widely used in telecoms equipment and computing.
Binary is the simplest kind of number system that uses only two digits of 0 and 1. By using these digits computational problems can be solved by machines because in digital electronics a transistor is used in two states. Those two states can be represented by 0 and 1. That is why this number system is the most preferred in modern computer engineer, networking and communication specialists, and other professionals. Read More
In cryptography, a keyed-hash message authentication code (HMAC) is a specific type of message authentication code (MAC) involving a cryptographic hash function and a secret cryptographic key. It may be used to simultaneously verify both the data integrity and the authentication of a message, as with any MAC. Any cryptographic hash function, such as MD5 or SHA-1, may be used in the calculation of an HMAC; the resulting MAC algorithm is termed HMAC-X, where X is the hash function used (e.g. HMAC-MD5 or HMAC-SHA1). The cryptographic strength of the HMAC depends upon the cryptographic strength of the underlying hash function, the size of its hash output, and the size and quality of the key. HMAC generation uses two passes of hash computation. The secret key is first used to derive two keys – inner and outer. The first pass of the algorithm produces an internal hash derived from the message and the inner key. The second pass produces the final HMAC code derived from the inner hash result and the outer key. Thus the algorithm provides better immunity against length extension attacks. An iterative hash function breaks up a message into blocks of a fixed size and iterates over them with a compression function. For example, MD5 and SHA-1 operate on 512-bit blocks. The size of the output of HMAC is the same as that of the underlying hash function (e.g., 128 or 160 bits in the case of MD5 or SHA-1, respectively), although it can be truncated if desired. HMAC does not encrypt the message. Instead, the message (encrypted or not) must be sent alongside the HMAC hash. Parties with the secret key will hash the message again themselves, and if it is authentic, the received and computed hashes will match. Read More