this script finds the checksum value of any application… given that that application allows such actions to be submitted upon it.
set a to choose file
set b to POSIX path of a
set c to do shell script "md5 '" & b & "'"
set e to info for a
if c = "" then
display dialog "MD5 for " & name of e & ":" & return & "This operaton was not permitted by " & name of e buttons {"Choose Application", "Cancel"} default button 1
else
display dialog "MD5 for " & name of e & ":" & return & last word of c
end if