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Verification Code Generation

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Java - import sun.misc.BASE64Encoder got error in Eclipse. XOR operation with two strings in java.

Hash algorithms

Random String Generation. Security token. A security token (or sometimes a hardware token, authentication token, USB token, cryptographic token, software token, virtual token, or key fob) may be a physical device that an authorized user of computer services is given to ease authentication. The term may also refer to software tokens. Security tokens are used to prove one's identity electronically (as in the case of a customer trying to access their bank account). The token is used in addition to or in place of a password to prove that the customer is who they claim to be.

The token acts like an electronic key to access something. Some may store cryptographic keys, such as a digital signature, or biometric data, such as fingerprint minutiae. Some designs feature tamper resistant packaging, while others may include small keypads to allow entry of a PIN or a simple button to start a generating routine with some display capability to show a generated key number. Password types[edit] Static password token. Physical types[edit] Hash chain. Definition[edit] A hash chain is a successive application of a cryptographic hash function to a string For example, gives a hash chain of length 4, often denoted Applications[edit] Lamport[1] suggested the use of hash chains as a password protection scheme in an insecure environment.

Which is provided by the user. To the server. And verifies this matches the hash chain it has stored. For the next time the user wishes to authenticate. An eavesdropper seeing communicated to the server will be unable to re-transmit the same hash chain to the server for authentication since the server now expects . Binary hash chains[edit] Binary hash chains are commonly used in association with a Hash tree. The above diagram shows a hash tree consisting of eight leaf nodes and the hash chain for the third leaf node. See also[edit] References[edit] Jump up ^ L. Hash-based message authentication code. SHA-1 HMAC Generation. In cryptography, a keyed-hash message authentication code (HMAC) is a specific construction for calculating a message authentication code (MAC) involving a cryptographic hash function in combination with a secret cryptographic key. As with any MAC, it may be used to simultaneously verify both the data integrity and the authentication of a message.

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-MD5 or HMAC-SHA1 accordingly. The cryptographic strength of the HMAC depends upon the cryptographic strength of the underlying hash function, the size of its hash output, and on the size and quality of the key. 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. Definition (from RFC 2104)[edit] where H is a cryptographic hash function, | denotes concatenation, Algorithm - How to generate a verification code/number.