Cryptography is the branch of science dealing with the issues of secrecy of information through its encryption. Also, cryptography is referred to a set of methods for such secrecy. With cryptography you can convert normal plain text or other type of message in such a way that becomes unintelligible to unauthorized recipients. Appropriate recipient can transform received information back into readable form.
Cryptographic algorithm (cipher) is mathematical function used for encryption and decryption.
Encryption is a process in which a text message (plain text) is converted to an encrypted message. This process is performed using an encryption algorithm and the corresponding key. Decryption is the reverse operation to encryption - the encrypted message (cryptogram) is converted back to its original form.
Today, I will write about SHA1. It is a family of related cryptographic hash functions designed by the NSA (National Security Agency) and published by the National Institute of Standards and Technology. The first one was published in 1993 and officially called SHA (unofficially, not to be confused with the successors referred to as SHA-0). SHA1 was published in 1995 and completely replaced the withdrawn (due to officially undisclosed defects) with use of SHA-0. SHA-0 and SHA-1 form 160-bit digest of messages with a maximum size of 264 bits and is based on similar principles as MD5. SHA-1 algorithm should not be used in new applications. The primary purpose of the publication of the SHA was an American Standard Digital Signature (Digital Signature Standard). SHA is the foundation block cipher SHACAL. Successful attacks on hash functions having a structure similar to the SHA-1 was reported in 2004. It has raised the issue of long-term security of SHA-1. Between 2005 and 2008 series of attacks were published, both on a simplified version of SHA-1 and complete. The best of these attacks requires only about 263 compression function operations (compared to 280 a brute-force). NIST announced that the 2010 cease use SHA-1 for the different variants of SHA-2.