Cryptography-Digest Digest #234, Volume #14 Wed, 25 Apr 01 19:13:00 EDT
Contents:
Re: First analysis of first cipher ("Tom St Denis")
Re: hellman ("Tom St Denis")
Re: Censorship Threat at Information Hiding Workshop (David Wagner)
Re: Micro Video Camera Suitable for Documents? (John Savard)
Re: What Is the Quality of Randomness? (John Savard)
Re: Censorship Threat at Information Hiding Workshop (David Wagner)
Re: OTP WAS BROKEN!!! (newbie)
Re: What Is the Quality of Randomness? ("Mark G Wolf")
Re: What Is the Quality of Randomness? ("Tom St Denis")
Re: What Is the Quality of Randomness? ("Mark G Wolf")
Re: Micro Video Camera Suitable for Documents? (Mok-Kong Shen)
Re: compare PRNG (Tim Tyler)
Re: What Is the Quality of Randomness? ("Tony T. Warnock")
Re: What Is the Quality of Randomness? ("Tom St Denis")
Re: What Is the Quality of Randomness? (John Savard)
Re: Micro Video Camera Suitable for Documents? (Paul Rubin)
Re: Micro Video Camera Suitable for Documents? (Paul Rubin)
Re: Censorship Threat at Information Hiding Workshop ("Roger Schlafly")
Re: What Is the Quality of Randomness? (John Savard)
Re: What Is the Quality of Randomness? ("Mark G Wolf")
Re: What Is the Quality of Randomness? ("Mark G Wolf")
Re: What Is the Quality of Randomness? ("Tom St Denis")
----------------------------------------------------------------------------
From: "Tom St Denis" <[EMAIL PROTECTED]>
Subject: Re: First analysis of first cipher
Date: Wed, 25 Apr 2001 21:10:06 GMT
<[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED]...
> Mark Wooding wrote:
> >
> > [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
> >
> > > Last week I posted my first cipher (now dubbed "Brontosaurus") and
> > > was challeged to cryptanalyze it. Once again, point out WHY I'm going
> > > wrong as well as where:
> >
> > <grin>
> >
> > > The short analysis is that Bronto will be "easily" broken using
> > > differential cryptanalysis techniques. The primary weakness of the
> > > cipher is that S-boxes with 4-bit entries, chosen at random, are
> > > used. At this point, I think that the weakness is due primarily to the
> > > small m, and not necessarily due to the fact that the entries are
> > > randomly chosen.
> >
> > With an S-box that small, you must choose it carefully, rather than
> > trusting to luck.
> >
>
> I've seen some papers discussing the use of bent functions to generate
> strong S-boxes. Other papers discuss Hadamard matrices. What are the
> other common methods of generating strong S-boxes.
Bent functions are bad ideas. They are not bijective and generally I think
any function that loses information is a bad idea.
You can also use GF inversion, feistel networks, sp networks..
> > > Since the S-boxes are the only part of the cipher which provides
> > > non-linearity, the strength of the cipher depends almost entirely on
> > > the strength of the S-boxes.
> >
> > No. Everything there has an important function. Each component is weak
> > in isolation. You must combine them together so that they strengthen
> > each other. A cipher is an ensemble piece.
>
> It seems to me that the P-boxes (which provide "diffusion") are only
> there
> to support the S-boxes i.e. to ensure that different S-boxes are used
> rather
> than the same S-box being used over and over. A P-box alone doesn't
> provide
> "security" but an S-box by itself does, provided it is large enough. A
> block cipher
> simply mimics a large S-box. I think a cipher with strong S-boxes and
> weak
> P-boxes would be better than a cipher with weak S-boxes and good
> P-boxes.
> Granted, as you said, ideally every component should be optimized.
DES like designs are stupid. They lack formal proofs of security. Current
trends are more towards mathematical designs instead of wild bit
permutations (i.e ICE, DES, etc...)
Tom
------------------------------
From: "Tom St Denis" <[EMAIL PROTECTED]>
Subject: Re: hellman
Date: Wed, 25 Apr 2001 21:10:45 GMT
"Michael Scott" <[EMAIL PROTECTED]> wrote in message
news:d_GF6.180280$[EMAIL PROTECTED]...
> Because its faster. There are two types of attack on the discrete
logarithm
> problem. One (Index calculus) exploits the small size of p, the other
(e.g.
> Pollard Rho, Pollard Lambda) exploits the small size of the exponent. They
> both have quite different complexities. If you use Elliptic curves index
> calculus methods don't apply, and hence a much smaller prime modulus p can
> be used here as well. If you use an exponent of 160 bits, the best
discrete
> logarithm attacks have a complexity of about 2^80 steps - which is
reckoned
> to be infeasible.
Ah gotcha.
Tom
------------------------------
From: [EMAIL PROTECTED] (David Wagner)
Subject: Re: Censorship Threat at Information Hiding Workshop
Date: 25 Apr 2001 21:27:40 GMT
John Myre wrote:
>Emotional use of terminology is an old political trick, but it
>seldom works to complain about it. If it isn't "theft", what
>is it? "Uncompensated copying" is just rhetoric in the opposite
>direction. (It might help to distinguish cases. Where is the
>boundary between "theft" and not?)
Call it criminal copying if you like. But the point is that the reasons
why criminal copying is, well, criminal are not exactly the same reasons
why criminal theft is criminal, and the tradeoffs may be different in
important cases.
For instance, if we view copyright as a tool intended for the common
good, then "theft" (i.e., uncompensated copying) might be in some cases
beneficial, if it benefits the public good. Examples of this include
parody, fair use, and so on. So the emotional baggage that comes with
the word "theft" might lead you astray if you are not extremely careful
in how you use it.
------------------------------
From: [EMAIL PROTECTED] (John Savard)
Subject: Re: Micro Video Camera Suitable for Documents?
Date: Wed, 25 Apr 2001 21:29:57 GMT
On Wed, 25 Apr 2001 22:39:41 +0200, Mok-Kong Shen
<[EMAIL PROTECTED]> wrote, in part:
>One reads in Kahn's book about the micro dots of WWII. How
>does that compares with the modern technology in photography?
Here, we're talking CCDs. Microdots used light-sensitive dyes, and
thus were like blueprints, not photographs - they needed to be
prepared over very long exposure times under very bright lights.
They can achieve fantastic resolutions.
John Savard
http://home.ecn.ab.ca/~jsavard/crypto.htm
------------------------------
From: [EMAIL PROTECTED] (John Savard)
Subject: Re: What Is the Quality of Randomness?
Date: Wed, 25 Apr 2001 21:32:34 GMT
On Wed, 25 Apr 2001 15:28:11 -0500, "Mark G Wolf"
<[EMAIL PROTECTED]> wrote, in part:
>I'm trying to find out if given a choice of several different pieces of
>cipher key, which do I choose to best encrypt a message.
If someone else gave them to you, they're all bad choices. He can read
your message with any of them.
If you made them yourself with a physical noise source, just XOR them
all together to improve the quality. Or use a method like
00 - ignore
01 - 0
10 - 1
11 - ignore
that removes bias.
Using a test, and picking the 'best' one each time, only puts a
constraint on your key pages, and makes the result *less* random.
John Savard
http://home.ecn.ab.ca/~jsavard/crypto.htm
------------------------------
From: [EMAIL PROTECTED] (David Wagner)
Subject: Re: Censorship Threat at Information Hiding Workshop
Date: 25 Apr 2001 21:32:09 GMT
Terry Ritter wrote:
>If you don't like the word "theft" because you think it biased,
>presumably you have a better word in mind. But what would that word
>be?
How about "prohibited copyright infringement" or somesuch?
It is not so hard to be precise in your meaning.
The point is that when you say "copyright theft is wrong", the
risk is that all of the weight of the argument is carried by the
emotional overtones of the word "theft", when the argument that
"criminal theft is wrong" should instead be based on arguments
that, for instance, "criminal theft" is detrimental to the common
good.
(Quite possibly the common good is best served by ensuring that
authors get paid for their work and thus by making uncompensated
copying illegal, but this is a very different argument than saying
that "it is theft and therefore wrong for the same reason that
stealing someone's property is wrong".)
Emotion-laden words and questionable analogies often stand in the
way of dispassionate analysis, so we should be prepared to be suspicious
of them if they seem to be getting in the way.
------------------------------
From: newbie <[EMAIL PROTECTED]>
Subject: Re: OTP WAS BROKEN!!!
Date: Wed, 25 Apr 2001 17:33:51 -0300
Let analyze the first bit.
The sender, when writing, its message has a probability NOT EQUAL TO 1/2
to write 1 rather than 0 or 0 rather than 1.
It is very simple.
Let suppose that the probability that the sender start its letter with
the letter "I" is quite near to 1 and the first bit of "I" is 1.
Let suppose that my keystream start with "K" unknown value.
If I know C(1), let suppose C(1)= 1, I can conclude that k(1)= 0 with
the same probability of the first bit of "I".
So, if I compute all the bits for all the message, I will obtain a
keystream with n bits wrong et m bit right. The percentage a "truth" ( k
estimated and real k ) is equal m/(n+m). If my guess and my statistics
are correct, k estimated will be quite equal to the real k that the
sender used.
Once, I obtain k estimated, I can compute another random bit-string
(Plaintext).
This random bit-string has individual probabilities for each position.
Those probabilities are nothing than the probability that n-th bit is
equal to 0 or 1.
My table :
Position 1 2 3 4 and so on....
bit 1 (%)64 45 67 48 and so on
bit 0 36 55 33 42 and so on
Plaintext
estimated 1 0 1 0 .....
When the probability that 1 occur is very important (65 %), I consider
that the value of the position is 1.
Same thing for 0.
When they are equal or near (48-42), I use random bit-string to decide.
My plaintext will be revealed little by little.
All my idea is based on the "predictable behaviour of the sender".
And the goal is to try to isolate randomness.
John Savard wrote:
>
> On Wed, 25 Apr 2001 12:57:54 -0300, newbie <[EMAIL PROTECTED]>
> wrote, in part:
>
> >I can still convert those words to bit-strings.
> >Do you agree with that statement?
> >If yes, I continue.
>
> That isn't the hard part.
>
> >My idea is that even if that the statement C= any P Xor K (as
> >"complement") can not be mathematically "broken", the probability of any
> >bit of P (depending on its position) is not equiprobable. My goal is to
> >exploit that difference.
>
> Since you know C, it is indeed also true that K is no longer
> equiprobable. It conforms, now, to the probability distribution of P,
> because you know C.
>
> But you can go *no further*.
>
> >So you can still deduce the "randomness" of the key.
>
> >You are going to obtain if you compute "pattern" Xor Ciphertext = random
> >key really used (this key is unique for the sender).
> >This key is not hundred per cent the sender used, but 75% or less.
>
> >If I have the quite-true key, I can use a controlled random key for my
> >plain-text to try to recover the plaintext that have more signification
> >given the context.
>
> I don't understand these three paragraphs at all.
>
> >I'm waiting for comments.
> >I know that I'm trying to find the "impossible".
>
> You can take our word for it that it _is_ impossible. Your first
> attempt did show the kind of technique which could be used if K was
> not truly random, and similar techniques are possible when the same K
> is used twice.
>
> I am sorry, but I do not believe you can receive here any responses
> that you will find genuinely useful. If after re-thinking, you still
> think you have something, try explaining it very carefully and
> plainly. Then it might be possible to explain what we think is the
> specific flaw. Otherwise, there is not much that can be done.
>
> John Savard
> http://home.ecn.ab.ca/~jsavard/crypto.htm
------------------------------
From: "Mark G Wolf" <[EMAIL PROTECTED]>
Subject: Re: What Is the Quality of Randomness?
Date: Wed, 25 Apr 2001 16:41:01 -0500
> For example, in a bit stream that is known to repeat the sequence
> '110110110010' endlessly, there is no randomness even though 110 occurs
more
> frequently than 010.
Exactly, now we're getting somewhere. Let's say we take some less than
"perfect" random sequence, we'll agree that 0 and 1 repeat often, obviously.
So does 00, 01, 10, 11, obviously. So does 000, 010, 110, etc. How about
101010101 and 101001100010110110101 ? Now these should occur a lot less
since they are longer sequences. My somewhat absurd question is, what's
more random given a finite sequence, longer groupings that occur more often
but have less predictable "sub" groups, or shorter groupings that have very
regular patterns but occur less often? Both groups occurring at equally
unpredictable intervals. I realize that question kind of "folds" in on
itself. But one would think that in a truly random sequence, the longer the
grouping the less likely it is to repeat again. What's the mathematical
relationship that brings those two extremes into "balance".
------------------------------
From: "Tom St Denis" <[EMAIL PROTECTED]>
Subject: Re: What Is the Quality of Randomness?
Date: Wed, 25 Apr 2001 21:47:07 GMT
"Mark G Wolf" <[EMAIL PROTECTED]> wrote in message
news:9c7gbc$4hq8$[EMAIL PROTECTED]...
> > For example, in a bit stream that is known to repeat the sequence
> > '110110110010' endlessly, there is no randomness even though 110 occurs
> more
> > frequently than 010.
>
> Exactly, now we're getting somewhere. Let's say we take some less than
> "perfect" random sequence, we'll agree that 0 and 1 repeat often,
obviously.
> So does 00, 01, 10, 11, obviously. So does 000, 010, 110, etc. How about
> 101010101 and 101001100010110110101 ? Now these should occur a lot less
> since they are longer sequences. My somewhat absurd question is, what's
> more random given a finite sequence, longer groupings that occur more
often
> but have less predictable "sub" groups, or shorter groupings that have
very
> regular patterns but occur less often? Both groups occurring at equally
> unpredictable intervals. I realize that question kind of "folds" in on
> itself. But one would think that in a truly random sequence, the longer
the
> grouping the less likely it is to repeat again. What's the mathematical
> relationship that brings those two extremes into "balance".
Your talking about bitstrings so a uniformly distributed N-bit sequence
should occur with a probability of 2^-N.
Tom
------------------------------
From: "Mark G Wolf" <[EMAIL PROTECTED]>
Subject: Re: What Is the Quality of Randomness?
Date: Wed, 25 Apr 2001 17:00:05 -0500
> Your talking about bitstrings so a uniformly distributed N-bit sequence
> should occur with a probability of 2^-N.
Ok, that actually answered my question. 0 or 1 should obviously occur 1/2
the time, just as any particular 2-bit sequence should occur 1/4 of the
time, if I picked any two bits at random. I was also trying to steer
towards another response. Of the two extremes, which would be "worse"?
------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Subject: Re: Micro Video Camera Suitable for Documents?
Date: Thu, 26 Apr 2001 00:05:34 +0200
John Savard wrote:
>
> On Wed, 25 Apr 2001 22:39:41 +0200, Mok-Kong Shen wrote:
>
> >One reads in Kahn's book about the micro dots of WWII. How
> >does that compares with the modern technology in photography?
>
> Here, we're talking CCDs. Microdots used light-sensitive dyes, and
> thus were like blueprints, not photographs - they needed to be
> prepared over very long exposure times under very bright lights.
>
> They can achieve fantastic resolutions.
I suppose that in any case all techniques have advanced
with time. BTW, people in nanotechnology are certainly
working in smaller scales. I guess that their knowledge
could well find applications in crypto.
M. K. Shen
------------------------------
From: Tim Tyler <[EMAIL PROTECTED]>
Subject: Re: compare PRNG
Reply-To: [EMAIL PROTECTED]
Date: Wed, 25 Apr 2001 22:01:37 GMT
M.S. Bob <[EMAIL PROTECTED]> wrote:
: ink wrote:
:> "Tom St Denis" <[EMAIL PROTECTED]> schrieb im Newsbeitrag
:> > "Dobs" <[EMAIL PROTECTED]> wrote in message news:9c1hkn$9c8$[EMAIL PROTECTED]...
:> > > How can I decide that one PRNG is better and more secure than other
:> >
:> > You analyze the algorithm not the output.
:>
:> C'mon... instead of just critizising, mention DieHard. That will at least
:> give *some* indication on how *good* or random the output of a PRNG
: No it doesn't. [...]
Diehard can be a useful indicator of *in*security - in that repeatable
failures of Diehard's tests is generally an indication of insecurity - if
they come from outputs that might otherwise be expected to be random.
: True random numbers may fail the test [...]
Yes, like with one chance in ten billion billion billion. Any
suspicious-looking failures can be examined further by retesting,
reducing the probability of false positives still further.
--
__________
|im |yler Try my latest game - it rockz - http://rockz.co.uk/
------------------------------
From: "Tony T. Warnock" <[EMAIL PROTECTED]>
Subject: Re: What Is the Quality of Randomness?
Date: Wed, 25 Apr 2001 16:10:09 -0600
Reply-To: [EMAIL PROTECTED]
The Quality of Randomness is not Strained.
------------------------------
From: "Tom St Denis" <[EMAIL PROTECTED]>
Subject: Re: What Is the Quality of Randomness?
Date: Wed, 25 Apr 2001 22:11:05 GMT
"Mark G Wolf" <[EMAIL PROTECTED]> wrote in message
news:9c7hf7$3asa$[EMAIL PROTECTED]...
> > Your talking about bitstrings so a uniformly distributed N-bit sequence
> > should occur with a probability of 2^-N.
>
> Ok, that actually answered my question. 0 or 1 should obviously occur 1/2
> the time, just as any particular 2-bit sequence should occur 1/4 of the
> time, if I picked any two bits at random. I was also trying to steer
> towards another response. Of the two extremes, which would be "worse"?
If you picked two bits at random you should get 00 01 10 and 11 with equal
probability. What else can I say?
>
>
>
------------------------------
From: [EMAIL PROTECTED] (John Savard)
Subject: Re: What Is the Quality of Randomness?
Date: Wed, 25 Apr 2001 22:12:24 GMT
*Every* N bit sequence has a probability of 2^(-N).
Hence, there is no objective answer to your question. But we can
decide, in terms of what looks obviously nonrandom to our subjective
eyes, that
1011010001101010
is 'more random' than either
1111111111111111
or
1111111100000000
or even
0101010101010101
but that's just a matter of opinion.
John Savard
http://home.ecn.ab.ca/~jsavard/crypto.htm
------------------------------
From: Paul Rubin <[EMAIL PROTECTED]>
Subject: Re: Micro Video Camera Suitable for Documents?
Date: 25 Apr 2001 15:16:16 -0700
[EMAIL PROTECTED] (MrDbol) writes:
> I need a micro video camera that can clearly capture text (every
> single letter) on a document from reading distance (1-2ft). For
> example, you sit down and you sign a contract and you have the
> camera on your chest, I want the camera to be able to capture every
> single letter, and the whole page legibly so that it can clearly be
> read and understood when it is played back on the VCR. Which
> micro-video camera do you recommend? Which micro-video camera do I
> need?
If you mean you want to surreptitiously record all the fine print in
the contract at the time that you sign it, that's pretty hopeless with
commonly available equipment. But why on earth are you going to sign
something where they don't give you a copy? Just ask them to make a
copy for you.
If you don't need to be surreptitious, you can make readable copies
with a conventional camera or digicam. I do this pretty often with my
Canon S100 digital Elph. This is a 2 megapixel digicam the size of a
pack of cigarettes. If I just want to copy a page or two, I get
readable results handholding the camera being reasonably careful to
hold it steady (I don't use the flash because that causes glare from
the page) . If I want more consistent results, I have a small
portable copy stand which I can take with me (e.g. to the library).
I can attach the S100 to the stand with filter adapter rings, or just
hold it on top of the stand with my hand.
I have some pictures of the copy stand at
http://www.nightsong.com/photo/copi-pod.html
if you want to see what it looks like.
------------------------------
From: Paul Rubin <[EMAIL PROTECTED]>
Subject: Re: Micro Video Camera Suitable for Documents?
Date: 25 Apr 2001 15:22:00 -0700
Mok-Kong Shen <[EMAIL PROTECTED]> writes:
> > Here, we're talking CCDs. Microdots used light-sensitive dyes, and
> > thus were like blueprints, not photographs - they needed to be
> > prepared over very long exposure times under very bright lights.
> >
> > They can achieve fantastic resolutions.
>
> I suppose that in any case all techniques have advanced with
> time. BTW, people in nanotechnology are certainly working in smaller
> scales. I guess that their knowledge could well find applications in
> crypto.
Microdots are actually kind of a lost art. They used a lot of
dangerous chemicals (aniline dyes containing cyanide, some other stuff
that happens to also be explosive, etc). Some people fool around with
microdots made with reversed microscopes and conventional photographic
materials (high-res film), but still with much lower magnification
than "spy" microdots.
------------------------------
From: "Roger Schlafly" <[EMAIL PROTECTED]>
Subject: Re: Censorship Threat at Information Hiding Workshop
Date: Wed, 25 Apr 2001 21:14:16 GMT
"David Wagner" <[EMAIL PROTECTED]> wrote in message
news:9c7fop$md9$[EMAIL PROTECTED]...
> Terry Ritter wrote:
> >If you don't like the word "theft" because you think it biased,
> >presumably you have a better word in mind. But what would that word
> >be?
> How about "prohibited copyright infringement" or somesuch?
> It is not so hard to be precise in your meaning.
While you are choosing terms, make sure you agree on what they mean.
The terms "murderer" and "killer" mean different things, and so do
"copier", "infringer", "thief", etc.
Eg, consider the following story from today's news. I wouldn't call what the
Sopranos did either theft or "prohibited copyright infringement" because
the issue is under dispute. It is alleged infringement, at best.
Perhaps some will think that it is theft for me to post this story. A better
term might be to say that it is an unlicensed copy.
http://home.abc28.com/Global/story.asp?S=313656&nav=0zGK2RaY
Ex-wiseguy says `Sopranos' stole from his book
Newark, New Jersey-AP -- A real-life former wiseguy from New Jersey is
crying copyright infringement over the H-B-O series "The Sopranos."
George Fresolone claims Sopranos creator David Chase used material from his
book, "Blood Oath," in an episode titled "Fortunate Son." That was the
segment where Tony Soprano's nephew was initiated into the mob.
Fresolone's lawyer has suggested a 125-thousand-dollar "settlement fee."
H-B-O denies anything was lifted from the book.
Fresolone says he and H-B-O staffers met last year and he was paid a one-day
consulting fee of two-thousand dollars.
The former member of the Newark branch of the Philadelphia mob is now in the
witness protection program. His testimony helped convict more than 40
mobsters.
------------------------------
From: [EMAIL PROTECTED] (John Savard)
Subject: Re: What Is the Quality of Randomness?
Date: Wed, 25 Apr 2001 22:33:04 GMT
On Wed, 25 Apr 2001 16:10:09 -0600, "Tony T. Warnock"
<[EMAIL PROTECTED]> wrote, in part:
>The Quality of Randomness is not Strained.
As I said:
<quote>
The quality of randomness cannot be established by putting the
generated digits through a sieve of statistical tests. Instead,
randomness comes from true physical sources like the rain from the
clouds in the sky...
Sorry, I couldn't resist.
<unquote>
so I thought of that joke first!
(The quality of mercy is not strain'd. It droppeth as the gentle rain
from heaven upon the place beneath: it is twice blest; it blesseth him
that gives and him that takes: ... The Merchant of Venice, Act IV,
Scene I.)
John Savard
http://home.ecn.ab.ca/~jsavard/crypto.htm
------------------------------
From: "Mark G Wolf" <[EMAIL PROTECTED]>
Subject: Re: What Is the Quality of Randomness?
Date: Wed, 25 Apr 2001 17:39:55 -0500
> *Every* N bit sequence has a probability of 2^(-N).
In a "perfectly" random distribution yes, but this is less than "perfect".
What I'm trying to get at is this, what bearing would the data to be
encrypted have on the security of the ciphertext. For instance, what if I
encrypted nothing but a sequence of A's in the form of 7-bit ASCII ?
------------------------------
From: "Mark G Wolf" <[EMAIL PROTECTED]>
Subject: Re: What Is the Quality of Randomness?
Date: Wed, 25 Apr 2001 17:51:37 -0500
> The Quality of Randomness is not Strained.
I wonder about that, since I have often observed the non-strained to be very
predictable.
------------------------------
From: "Tom St Denis" <[EMAIL PROTECTED]>
Subject: Re: What Is the Quality of Randomness?
Date: Wed, 25 Apr 2001 22:59:27 GMT
"Mark G Wolf" <[EMAIL PROTECTED]> wrote in message
news:9c7jpi$87ee$[EMAIL PROTECTED]...
> > *Every* N bit sequence has a probability of 2^(-N).
>
> In a "perfectly" random distribution yes, but this is less than "perfect".
>
> What I'm trying to get at is this, what bearing would the data to be
> encrypted have on the security of the ciphertext. For instance, what if I
> encrypted nothing but a sequence of A's in the form of 7-bit ASCII ?
It would still be random if your source for encrypting was random. I.e if
you take an OTP to a string of zeroes it's still random. If you know as an
attacker beforehand that the plaintext is all zeroes then the plaintext is
not random, no shit, but that's not the point. The point of encrypting
something is to hide non-trivial knowledge.
Tom
------------------------------
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