Verified answer

In other words. MD5 is an algorithm that was made to

encrypt or "hash" a string or even whole files. The MD5

hash is always the same length such as the 40 character

string.

Hello World! after it has been MD5 hashed looks like:

ed076287532e86365e841e92bfc50d8c

A file that's 20mb in size looks like:

a8f5f167f44f4964e6c998dee827110c

Just like the other guy mentioned you would mostly use

this to help with file comparisons. If you get the MD5 hash

of a file and then alter it. The MD5 hash will not be the

same. So if you send your friend a program and you get the

MD5 hash. He can then do the same when he receives the

whole file. If they are different then the file you sent him is

different.

Also the reason why you can't "undo" MD5 is because

it's a 1-way encryption. It's meant to not be cracked.

Other encryption methods such as SHA-1 and SHA-2

have been cracked in the past and don't fairly match

up o MD5.

That's about as simple as I can put it.

- Hex

It isn't a one-for-one cypher. It is a result cypher - it can take in anything from a single character to a full book - but it always creates the same length of cypher - like a 40 byte string.

And yes - putting the same "thing" in gets the same result. That is what it is primarily used for - detection of changes. If I MD5 a file on your pc, then up-load it, then MD5 the file on the server, I can compare the 2 MD5 keys - if they match, I got the file perfectly - no "man in the middle" attack touched it.

But since it is a rolling result cypher, there is no way of knowing what went into making it up.