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Recent Announcements:
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11 Dec. The time and place for the review
session is 2:30-3:45 pm, Sunday, December 14, in AKW
500 (our regular classroom). Please make sure your
Yale ID cards are valided for after-hours building
access or else make other arrangements to get in
since AKW is locked on weekends.
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11 Dec. Several announcements:
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The final
exam will be given on Monday, December 15,
at 2:00 pm in room LC 317. Note
that "LC" refers to "Linsly-Chittenden Hall, 63
High St", which is on Old Campus. (In case of any
discrepancy, the
Yale College Fall 2008 Exam Schedule is
authoritative.)
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The final is a "2-hour" exam, which means you
will be given 2 1/2 hours to work it. Format will
be like the midterm: some choice of problems,
closed book, calculators permitted but no PDA's,
laptops, or other devices with text storage
capabilities, graphing calculators are okay if
the memory is cleared before the exam --- check
this out with the TA before the start of the
exam.
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Study guide for
final examination (.pdf) is now
available.
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The TA will hold a review session on Sunday,
Dec. 14, at a time and place to be announced.
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9 Dec. Notes for yesterday's lecture 24 are now
available.
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2 Dec. Problem
Set 7 (.pdf) is available. It
is due before midnight on Friday, December 12.
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1 Dec. Material on today's lecture on
pseudorandom sequence generation is available in
lecture notes 22 and,
with somewhat greater detail, in handout 17.
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19 Nov. I thought you might be interested
in seeing cryptography in the making. The Technology
Review article,
"An Algorithm with No Secrets", describes the
process that is currently underway to replace the
current Secure Hash Algorithm 2 (SHA-2) with a newer,
more secure hash algorithm to be known as SHA-3.
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19 Nov. Problem
Set 6 (.pdf) is available. It
is due before midnight on Wednesday, December 3.
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17 Nov. The notes from last week's lecture 19 are available.
Section 85
corrects an error in the general chaining method that
I presented in class. The correct definition of
s1 is
h(0t0m1),
not
h(0t1m1)
as given in class. This correction is needed in case
2 of the proof.
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14 Nov. It seems that the posted sample
ciphertext file for PS5, cipher.txt , did
not correspond to the given key files. As some people
correctly pointed out, it was obviously bad since it
contained integers that were longer than the number
n in the public key file. I've replaced it
with a (hopefully) correct one.
Because of this error, I'm giving a 2-day
extension. The new due date for Problem Set
5 is before midnight on Sunday, November 16.
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11 Nov. Two remarks about problem set 5:
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I've placed some sample data in the Zoo course
directory
/c/cs467/assignments/ps5/ :
pub.txt |
sample public key |
priv.txt |
sample private key |
plain.txt |
sample plain text file (with
comments) |
cipher.txt |
sample cipher text file |
decrypted.txt |
result of decrypting
cipher.txt |
Note: Do not try to view these files with
your browser. They are not in HTML format, and
the whitespace used to separate numbers gets
lost. Rather, log into the Zoo and access them
directly.
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I did some more experiments with the openssl
BN_rand() function. I am happy to
report that it worked as advertised, including
for bit lengths less than 16. I don't know what
was going on when I observed the problems that I
reported in class yesterday, but probably my own
program had some bug that was causing
BN_rand() to misbehave or making me
think that it was misbehaving when it actually
wasn't. No matter, it does seem to be okay after
all.
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10 Nov. The security of QR Probabilistic
Encryption depends on the fact that the ciphertext is
chosen uniformly from
Qn11 when m=0 and
uniformly from Qn00 when
m=1. I revised the last paragraph of section
67 of lecture notes 15
(revision 2) to make this a little clearer.
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9 Nov. Xueyuan has prepared detailed
solutions to problem set
4 (.pdf).
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6 Nov. I fixed a typo in the definition of
discrete log. This was in section 58 of lecture notes 14, which now
stand at revision 2.
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5 Nov. Problem
Set 5 (.pdf) is available. It
is due before midnight on Friday, November 14. I also
corrected two links in lecture notes 13; hence, the
change in revision number.
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4 Nov. I've posted solutions to the midterm exam
(.pdf).
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4 Nov. I've posted notes for the last two lectures.
See Section
69 for the proof that I messed up in class of the
fact that if a is a quadratic residue modulo
both p and q, then it is a quadratic
residue modulo their product.
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28 Oct. The date of the final exam this
year, Dec. 15, falls on Monday, not Tuesday. Somebody
finally pointed out that it's been wrong on this web
site all term. I've corrected it below. Sorry for any
confusion.
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27 Oct. A minor error has been fixed in
solutions to problem set
3 (.pdf). The
handout number of the corrected version is #11 (rev.
2).
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27 Oct. Three brief announcements:
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Problem Set 4
(.pdf) is
available. It is due before midnight on Monday,
November 3.
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Xueyuan has prepared detailed solutions to problem set 3
(.pdf).
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Announcements prior to the midterm have been
moved to the Old
Announcements page.
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3 Sep. A final examination will be given at
the officially scheduled time, Monday,
December 15, 2:00 pm. Those enrolled under
the graduate number CPSC 567a are also expected to
take the final exam. Please
take this into account when making your end-of-term
travel plans. I do not plan to give an early
exam for the convenience of those who want to leave
campus early.
[Old Announcements]
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