Here is something I’ve thrown together:
on ShellEncryption(str, passwd, doEncode, isBase64)
-- echo 'plain text' | openssl enc -bf -pass pass:'my password' -salt -e
-- echo 'coded text' | openssl enc -bf -pass pass:'my password' -salt -d
-- The "echo" command apparently places its argument
-- into something called "standard input." The vertical
-- slash, ("pipe"), sends the standard input to the
-- next command
--
set src to "echo " & str's quoted form & " | "
-- "openssl" is a command line tool for implementing a
-- number of security operations. The "enc" indicates
-- that we want the encryption function of openssl.
--
set src to src & "openssl enc "
-- "enc" is followed by the encryption method to use.
--
-- The "man" says, "A beginner is advised to just use a
-- strong block cipher in CBC mode such as bf or des3."
--
-- "bf" indicates the Blowfish algorithm in CBC mode.
--
set src to src & "-bf "
-- Apparently, there are these "utilities" that can read
-- everything that happens in the command line, (Unix 'ps'
-- being an example). This makes the following method of
-- indicating the password insecure, (for people who are
-- running strange things with names like 'ps').
--
set src to src & "-pass pass:" & passwd's quoted form & " "
-- The "man" says "ALWAYS use -salt", whatever the heck it is.
--
set src to src & "-salt "
-- Encrypt or decrypt:
--
if (doEncode) then
set src to src & "-e " -- actually, it's the default
else
set src to src & "-d "
end if
-- For encryption, we're indicating if the result should be
-- returned in Base64 encoding. For decryption, we're
-- indicating if the encrypted string is in Base64, ie: it
-- needs to be decoded before it can be decrypted.
--
if (isBase64) then set src to src & "-a"
return do shell script src
end ShellEncryption
I was wondering if someone could explain to me about the password. The man page for enc(1) says that Blowfish takes a 128 bit key (16 bytes), by which I understood it to mean the password. Resources I found on the Internet indicate that Blowfish can use a key from 32 to 448 bits, (4 to 56 bytes). As it turns out, however, the command works without fail or complaint no matter what length password I use, including an empty string:
echo ‘hello’ | openssl enc -bf -pass pass:‘’ -salt -e | openssl enc -bf -pass pass:‘’ -salt -d
Why are the various pieces of documentation I’ve found not consistent with one another, and why would an encryption tool allow an empty password?
My ultimate goal would be a user-friendly AppleScript library implementing these 5 basic handlers:
EncryptText( theText, thePassword, useBase64 )
DecryptText( theText, thePassword, useBase64 )
EncryptFile( fileAlias, newFilePath, thePassword, useBase64 )
DecryptFile( fileAlias, newFilePath, thePassword, useBase64 )
FingerprintText( theText ) --> MD5 message digest
Before doing so, however, I want to be sure I understand the security issues involved. I’m not looking for something strong enough to keep out the NSA, but just a “reasonably secure” system for basic “good enough” encryption. The problem with the openssl command is that it has a million options, and despite the fact that “man” stands for “manual,” man has never satisfactorily explained anything to me.
