Application of hash algorithm: a fingerprint on a file so you can tell whether it has been altered, and the second is to conceal passwords so you can still recognize the correct password and enable login. SHA256 of the crypto algorithm used in bitcoin, blockchain ledger.
Example: Hello World! string input into the SHA256 function will output of hash value of 7F83B1657FF1FC53B92DC18148A1D65DFC2D4B1FA3D677284ADDD200126D9069.
Any changes or modification of Hello Word! the string will result in different has value output. Sending a message “Hello World!” with its hash value to the receiver. The receiver takes that message and runs it on the sha256 function to check the output hash match sender’s hash output value. The message gets authenticated receiver hash value match sender hash value.
Note: The sha256 function cannot take hash output value and return the original string value. The hash output value of the following 7F83B1657FF1FC53B92DC18148A1D65DFC2D4B1FA3D677284ADDD200126D9069 will not return “Hello World!” from sha256 function.
Online sha256 hash generator
Blockchain ledger and sha256 relationship
Blockchain is a chain of blocks, each block connects to another block via a sha256 value. Example. [block A data with sha256 value] connect to [block B data with block A sha256 value].
In node with two blockchains, to check ONLY change of data use the final block sha256 of the block B. The sha256 value does not match this could be the block A or final block B data altered. The blockchain has been compromised for a node, that node cannot be trusted in a network.