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diff --git a/doc/sha3sum.texinfo b/doc/sha3sum.texinfo
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@@ -61,14 +61,173 @@ Texts. A copy of the license is included in the section entitled
 @node Overview
 @chapter Overview
 
-Lorem Ipsum
+@command{sha3sum} is a collection of utilities
+around Keccak and its close derivatives SHA-3,
+SHAKE and RawSHAKE for calculating checksums
+and verifying the integrity of files.
+
+@command{sha3sum} is based on the library
+@command{libkeccak} which is not optimised for
+any particular microarchitecture. If you find
+a library optimised for your microarchitecture,
+not too much work should be required to make it
+@command{libkeccak}-compatible, if it isn't
+already; or alternatively, make @command{sha3sum}
+compatible with that library.
 
 
 
 @node Invoking
 @chapter Invoking
 
-Lorem Ipsum
+@command{sha3sum} include a collection of
+similar utilities:
+
+@table @command
+@item keccak-224sum
+Calculates Keccak-224 checksums,
+which is Keccak[r=1152,c=448,n=224].
+
+@item keccak-256sum
+Calculates Keccak-256 checksums,
+which is Keccak[r=1088,c=512,n=256].
+
+@item keccak-384sum
+Calculates Keccak-384 checksums,
+which is Keccak[r=832,c=768,n=384].
+
+@item keccak-512sum
+Calculates Keccak-512 checksums,
+which is Keccak[r=576,c=1024,n=512].
+
+@item keccaksum
+Calculates Keccak[] checksums,
+which is Keccak[r=1024,c=576,n=512].
+
+@item sha3-224sum
+Calculates SHA3-224 checksums.
+
+@item sha3-256sum
+Calculates SHA3-256 checksums.
+
+@item sha3-384sum
+Calculates SHA3-384 checksums.
+
+@item sha3-512sum
+Calculates SHA3-512 checksums.
+
+@item rawshake256sum
+Calculates RawSHAKE-256 checksums.
+
+@item rawshake512sum
+Calculates RawSHAKE-512 checksums.
+
+@item shake256sum
+Calculates SHAKE-256 checksums.
+
+@item shake512sum
+Calculates SHAKE-512 checksums.
+@end table
+
+The @command{sha3sum} utilities recognises the
+following options, and takes takes any number
+of files.
+
+@table @option
+@item --
+Parse all following arguments as filenames.
+
+@item ++
+Parse the next argument as a filename.
+
+@item -h
+@itemx --help
+Display a summary of options.
+
+@item -u
+@itemx --upper
+@itemx --uppercase
+@itemx --upper-case
+Output the checksums in upper case hexadecimal.
+
+@item -l
+@itemx --lower
+@itemx --lowercase
+@itemx --lower-case
+Output the checksums in lower case hexadecimal.
+
+@item -b
+@itemx --binary
+Output the checksums in binary format. When this
+is selected, no filenames or checksum delimiters
+are included in the output. Thus using this for
+more than one file will require some work.
+
+@item -x
+@itemx --hex
+@itemx --hex-input
+Input files are in hexadecimal rather than binary.
+
+@item -c
+@itemx --check
+Read checksums from the file and check them against
+the files on your systems. The input files files
+should be formated as the output of the
+@command{sha3sum} utilities when @option{--check}
+is not used, or similarly. This is not going to work
+if any of the filenames in the input files starts
+with a regular blank space or horizontal tab space,
+or if they contain a line feed, carriage return or
+form feed.
+
+@item -v
+@itemx --verbose
+Print extra information.
+@end table
+
+If no file is selected, or when @file{-} is used,
+standard input will be used.
+
+The utilities also support checking the parameters
+for the hash algorithm. These options are however
+only intended to be used with @command{keccaksum}
+unless stated otherwise.
+
+@table @option
+@item -R
+@itemx --bitrate
+@itemx --rate RATE
+Change the rate.
+
+@item -C
+@itemx --capacity CAPACITY
+Change the capacity.
+
+@item -N
+@itemx -O
+@itemx --output-size
+@itemx --output SIZE
+Change the output size.
+
+This should @emph{always} be specified when using
+@command{rawshake256sum}, @command{rawshake512sum},
+@command{shake256sum} and @command{shake512sum}.
+
+@item -S
+@itemx -B
+@itemx --state-size
+@itemx --state SIZE
+Change the state size.
+
+@item -W
+@itemx --word-size
+@itemx --word SIZE
+Change the word size.
+
+@item -Z
+@itemx --squeezes COUNT
+Change the number of squeezes that is performed.
+@end table