What is Checksum?

checksum is a function used to calculate some value for given data. As we see check is used to check given data with the calculated sum. Data may be little or very big like 1 MB, 10 MB, etc. but the checksum value will be the same size but different for each different type of data. the checksum is also called hash values.

Checksum Algorithms

There are a lot of algorithms used to calculate checksum or hash of given data. We can use following algorithms to calculate checksum.

• MD5 is the most popular checksum algorithm but it is currently assumed as insecure
• LM is Windows operating system based check algorithm which is used to calculate password checksum
• NTLM is an older version of the LM
• SHA1 is the generation and update of the MD5
• SHA256 provides longer checksum value than SHA1 and more secure.

Check algorithms generally used for data integrity and security. For example, a data part is checksum is calculated and data is traveled over the network and this data may be corrupt. To Be sure the data checksum is calculated again and controlled with provided checksum.

Checksum Example For Linux OpenSSL

There is a lot of different checksum tool which can be used for calculation. We can use OpenSSL in Linux operating system. In this example, we will calculate the checksum of the file named phpinfo.php file which contains some PHP code. We will provide sha1 option to the openssl command.

$ openssl sha1 phpinfo.php

Checksum Example For Windows

Windows also provide a checksum tool named certutil.exe natively. This tool can be used to calculated certificates and etc. too. We can use this tool to calcualte MD5 checksum of a given file like below.

> CertUtil -hashfile '.\Users\İsmail Baydan\Downloads\genymotion-2.12.1-vbox.exe' MD5