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Frequent Asked Questions (FAQs)
What checksum algorithms are currently implemented?
Currently, there are a total of thirteen different checksums implemented in version 2.1.
These include MD5, SHA1, SHA512, Whirlpool, GOST R 34.11-94 and RIPEMD320, among others.
Which is the best checksum to use?
It all depends on the application. In all cases, the security of the algorithm is
clearly the most important factor, but this is limited by how it will be applied.
If we are looking for a hash/checksum to protect the integrity of a very important
document, for example, we would need to opt for the largest hash we can find.
Using FireHash, this means we would be using SHA512 or Whirlpool.
Although, nowadays the speed of the algorithm is not a factor when deciding which
one to use, like it used to be, the length of the resulting hash might be. The
larger the hash the more troublesome its use can be. It is clearly easier to
make use of small resulting hashes, like the ones coming from SHA1 and RIPEMD160, than
that of larger ones. This problem is not as aparent when only dealing with one or
two hashes. But when dealing with dozens of them, speed and size become more and
more the deciding factor.
Which is the difference between a hash and a checksum?
None. They are one and the same. Hashes and checksums are also known as non-keyed
message digests.
How can I see the resulting hash without having to copy and paste it some
place else?
The easiest way to see a long resulting hash, like the one you would get from SHA512,
is by simply placing your mouse/cursor on top of the lower text box containing the
hash. With the cursor on top of the text box, a tooltip window will open
showing you the complete hash.
How can I generate a hash for a very large document?
When trying to generate the hash for a really large document, like 300MB, for example,
you will probably get an error coming from the Java Virtual Machine. The reason
for this is that Java tries to be nice and not over reserve big chucks of memory
at once. The problem here lies on the heap memory allocation. In short, we need
to select a larger chunk of heap memory for this type of operation than Java normally
allocates. We do this by starting FireHash from the command-line with a command
like the following:
java -Xms128m -Xmx512m -jar firehash.jar
This line is allocating a heap memory space between 128megs to 512megs, which would
be more than enough to generate a hash for a 300meg file. Change the "128m" and
the "512m," accordingly, based on the file size you are working with.
How come sometimes I cannot paste into other applications the hash I just
copied from FireHash?
As we know, the way to copy a hash generated in FireHash is by simply pressing the
Copy button within the application. This action copies the last generated hash into
the system clipboard, which means it will be available for other applications to use.
Ironically, depending on the given implementation, some applications will only
grab this information via the use of CTRL+V (pressing the Control and V keys)
combination, and not via its graphical interface. This is outside our control and it's
based on a particular system/application implementation.
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