Re: Tasking and Concurrent Programming Using Multiple Ada Programs.

[Dennis Lee Bieber <wlfraed@ix.netcom.com>]

On Sat, 29 Apr 2017 01:13:45 -0700 (PDT), Austin Obyrne
<austin.obyrne@hotmail.com> declaimed the following:

>The hoped for plan is to write a program that will cater for 36 (or less if needs be ) ciphers all reading in and immediately encrypting, in rotation from the same file of plaintext and writing out the resulting ciphertext to the same ciphertext file (the encrypted plaintext file).  They would of course be written in Ada.
>

	Insufficient problem description...

	Do you mean that each of the 36 is processing the identical input, and
the output is to be interleaved in the destination file? If so, what chunk
size, and is the order of interleaving important (if it is, you probably
won't gain too much from concurrency since your output needs to be
sequential -- so you end up waiting for #1 to return data before you can
even go on to waiting for #2's data, even if #2 finishes before #1.

	It also means your output file will be 36 times larger... And then you
have the decryption -- what are you going to do, feed each chunk, in order,
to separate decryption functions when all of them are going to produce the
identical plain-text... Lots of redundant processing on your end, while
supplying an attacker with 36 variant copies of the same text -- if they
can determine the chunk size (and depending upon algorithms, the encrypted
text may show some boundaries).

	OR is each of the 36 supposed to be working on a different chunk of the
source -- so the output file is the same size as the input? You've still
got the problem of having to produce the output in sequential order, so
there is lots of waiting for output to be available.

>What I would like to know is if some of your members are familiar with tasking and concurrent programming sufficient to be able to say - Yes, it is feasible at least and give any other advice you may have to offer.
>

	Sure it's possible... But is it effective and useful? Probably not.

{NOTE: I used the above text as the "plain.txt"}

	Python program (you didn't think I was going to write your Ada
template, did you?):

-=-=-=-=-=-

import threading
import Queue

CHUNKSIZE = 32

class Algorithm1(object):
    def __init__(self, increment):
        self.inc = increment
    def process(self, pbyte):
        return chr((ord(pbyte) + self.inc) % 256)

class Algorithm2(object):
    def __init__(self, increment):
        self.inc = increment
    def process(self, pbyte):
        if self.inc == 0: self.inc = 1
        cbyte = chr((ord(pbyte) + self.inc) % 256)
        self.inc = (self.inc * 2) % 256
        return cbyte

class EOD(object):
    pass

ALGORITHMS = [ Algorithm1(2), Algorithm2(2), Algorithm1(3), Algorithm2(3) ]

def process(alg, inQ, outQ):
    while True:
        data = inQ.get()
        if data == EOD:
            break
        else:
            odata = "".join([alg.process(d) for d in data])
            outQ.put(odata)

taskControl = []

for alg in ALGORITHMS:
    inQue = Queue.Queue()
    outQue = Queue.Queue()
    task = threading.Thread(target=process, args=(alg, inQue, outQue))
    task.start()
    taskControl.append( (task, inQue, outQue) )

fin = open("plain.txt", "rb")
fout = open("cypher.txt", "wb")

while True:
    data = fin.read(CHUNKSIZE)
##    print repr(data)
    if not data: break
    #   send CHUNKSIZE of data to each task to process
    for (t, iQ, oQ) in taskControl:
        iQ.put(data)

    #   wait for each task in sequence to return the processed chunk
    for (t, iQ, oQ) in taskControl:
        odata = oQ.get()
##        print repr(t), repr(odata)
        fout.write(odata)

#   send END OF DATA flag to each task
for (t, iQ, oQ) in taskControl:
    iQ.put(EOD)

#   join (termination) of tasks
for (t, iQ, oQ) in taskControl:
    t.join()

fout.close()
fin.close()
-=-=-=-=-=-=-

	And the output of running it (note -- the newsreader will likely have a
fit, though I'm copying from a text editor that shows non-printables as
inverse video expressions...

-=-=-=-=-=-=-
Qp"Ucv."4;"Crt"4239"23<35<67"/29Qr(c´¬!4=(Q² 325?0Pqº25><E@m°8Rq#Vdw/#5<#Dsu#534:#34=46=78#03:Rt,k‘Ôì 3;$I€’`²13;(@Qz±4<8=0Mp·22"*RFV+."Cwuvkp"Qd{tpg">cwuvkp024(8p„Ô*.$I…“´éo"Sj‰’®å!>e}ƒ”©î/33#+SGW,/#Dxvwlq#Re|uqh#?dxvwlq112$0`d”©-"E}ƒ”©î!Qf‚Ž¥ =cy{„‰®®qd{tpgBjqvockn0eqo@"fgenckogf"vjqf‚Ž¥Àiqxuq‰¬®dqqF0„¥ãmcmuu„`ôire|uqhCkrwpdl
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-=-=-=-=-=-


-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/