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Science Forum Index » Cryptography Forum » quizz...
Page 1 of 1
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| Author |
Message |
| Mido... |
 Posted: Tue Jul 08, 2008 9:56 am |
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Guest
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Hi,
well it's a quizz that i had in some security course in uni but i
couldnt and no one could help solving it so far!!
and here is the quizz
Alice >> Bob:
65537,376781096648655171476075046480384036003069767135878367046892404899787642486409
Bob >> Alice:
282833517591435239342270053773279218579315796727277426826963893552262154129057
038465481487634624354845048059184314627639662982706432909184536115489229069975
171303235680267287580845213988591987016737683250608291454783603000401455241565
Alice >> Bob:
hOt7FrXiOxhE9u8D0MzORMkzya6OxejiD0zM9EMav57s8jzYrECA1+9sop4XtY9LlXWi3KpAF49+OIFisSIW4HDI
Pkbt1vg/
0pL2DCAkHlRiSVUwzQnJ8LkomsiDg6ZxYklVMM0JyfC5KJrIg4OmcWJJVTDNCcnwuSiayIODpnFiSVUw
zQnJ8LkomsiDg6Zx8C3K9jXtqcuyerT8rdX7ULUFA3FfGRY9gNKJtF2G6s44r0dfp0lh6I5pvLUeoRmXDUNf4O3k
Cc/
B9vbfgluoY2W5T6F8uEewS66adCwS8R8Pw55pUODH5QEu05qr1IJD0J1q9tPLRPSMWDZEzoRq408b9ah8ka8f
ONOE1Zpd6k9mRG1f3hw9rU
+SA3eyay72KNmLr7jH4rKnDNGQs0PDIo7+hHZrYNkd3SQfQBTJy0Z/TR4VCnPXjID8
+P+Ml4ia+O4+0Y491NzSztLM605mai+AtPMrCb/WEsC/
Vv7mBq2TWJemcakUP5U4W3wLDUpz1kEVlf98cX3Pc9VA
VZp+sF4vGLaAKp+e9/mIAbFLPB01IOlzlpZJikpliPkMV6NNzPSSPLaSf5Rhi72XLOo
+f16i+mXOgTJYgC9snwnm
2/FyDu32MuMl9rcDjzjIShQDpmPF78oOeEzMSCVsMIpo0EK+qwS1QOySDZySUVpS
+gqMiacgDsdTsGBvk+MUiJeI
ohTZd3HMa0UwUW/eGo82d+t/9cEHFfwgv8WMuGJJd4/oPlgttNz/caRb6ih5VJ1vGY7uf0/
jngzF+ZZb1l5JSRez
Sv/vTk2iiOWwyjw7Y8pDMNhqRL
+zphCU3OH7znu64GXr1yRYOkIgXpfO2hET1ztm37CFEy5zHH5YfpogVPqKpF5p
XyVIMNnA9ATJ2Qjf9d0nyJZjVo7xHh
+gFTKmxMErUnXqxdL68PWQoRxSMd0J87L73aXJ1u0IovuqZbYu
---------------------------------------------------------------------------------------
i got some help from some friends here so i could get alice private
and public key while bob's keys are still undiscovered ..!!!!!! |
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| David Eather... |
| Posted: Tue Jul 08, 2008 4:45 pm |
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Guest
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Mido wrote:
Quote: Hi,
well it's a quizz that i had in some security course in uni but i
couldnt and no one could help solving it so far!!
and here is the quizz
Alice >> Bob:
65537,376781096648655171476075046480384036003069767135878367046892404899787642486409
Bob >> Alice:
282833517591435239342270053773279218579315796727277426826963893552262154129057
038465481487634624354845048059184314627639662982706432909184536115489229069975
171303235680267287580845213988591987016737683250608291454783603000401455241565
Alice >> Bob:
hOt7FrXiOxhE9u8D0MzORMkzya6OxejiD0zM9EMav57s8jzYrECA1+9sop4XtY9LlXWi3KpAF49+OIFisSIW4HDI
Pkbt1vg/
0pL2DCAkHlRiSVUwzQnJ8LkomsiDg6ZxYklVMM0JyfC5KJrIg4OmcWJJVTDNCcnwuSiayIODpnFiSVUw
zQnJ8LkomsiDg6Zx8C3K9jXtqcuyerT8rdX7ULUFA3FfGRY9gNKJtF2G6s44r0dfp0lh6I5pvLUeoRmXDUNf4O3k
Cc/
B9vbfgluoY2W5T6F8uEewS66adCwS8R8Pw55pUODH5QEu05qr1IJD0J1q9tPLRPSMWDZEzoRq408b9ah8ka8f
ONOE1Zpd6k9mRG1f3hw9rU
+SA3eyay72KNmLr7jH4rKnDNGQs0PDIo7+hHZrYNkd3SQfQBTJy0Z/TR4VCnPXjID8
+P+Ml4ia+O4+0Y491NzSztLM605mai+AtPMrCb/WEsC/
Vv7mBq2TWJemcakUP5U4W3wLDUpz1kEVlf98cX3Pc9VA
VZp+sF4vGLaAKp+e9/mIAbFLPB01IOlzlpZJikpliPkMV6NNzPSSPLaSf5Rhi72XLOo
+f16i+mXOgTJYgC9snwnm
2/FyDu32MuMl9rcDjzjIShQDpmPF78oOeEzMSCVsMIpo0EK+qwS1QOySDZySUVpS
+gqMiacgDsdTsGBvk+MUiJeI
ohTZd3HMa0UwUW/eGo82d+t/9cEHFfwgv8WMuGJJd4/oPlgttNz/caRb6ih5VJ1vGY7uf0/
jngzF+ZZb1l5JSRez
Sv/vTk2iiOWwyjw7Y8pDMNhqRL
+zphCU3OH7znu64GXr1yRYOkIgXpfO2hET1ztm37CFEy5zHH5YfpogVPqKpF5p
XyVIMNnA9ATJ2Qjf9d0nyJZjVo7xHh
+gFTKmxMErUnXqxdL68PWQoRxSMd0J87L73aXJ1u0IovuqZbYu
---------------------------------------------------------------------------------------
i got some help from some friends here so i could get alice private
and public key while bob's keys are still undiscovered ..!!!!!!
WTF can't you get Bob's public key? |
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| Douglas Eagleson... |
| Posted: Wed Jul 09, 2008 3:03 am |
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Guest
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On Jul 8, 12:56 pm, Mido <mideast3... at (no spam) gmail.com> wrote:
Quote: Hi,
well it's a quizz that i had in some security course in uni but i
couldnt and no one could help solving it so far!!
and here is the quizz
Alice >> Bob:
65537,376781096648655171476075046480384036003069767135878367046892404899787642486409
Bob >> Alice:
282833517591435239342270053773279218579315796727277426826963893552262154129057
038465481487634624354845048059184314627639662982706432909184536115489229069975
171303235680267287580845213988591987016737683250608291454783603000401455241565
Alice >> Bob:
hOt7FrXiOxhE9u8D0MzORMkzya6OxejiD0zM9EMav57s8jzYrECA1+9sop4XtY9LlXWi3KpAF49+OIFisSIW4HDI
Pkbt1vg/
0pL2DCAkHlRiSVUwzQnJ8LkomsiDg6ZxYklVMM0JyfC5KJrIg4OmcWJJVTDNCcnwuSiayIODpnFiSVUw
zQnJ8LkomsiDg6Zx8C3K9jXtqcuyerT8rdX7ULUFA3FfGRY9gNKJtF2G6s44r0dfp0lh6I5pvLUeoRmXDUNf4O3k
Cc/
B9vbfgluoY2W5T6F8uEewS66adCwS8R8Pw55pUODH5QEu05qr1IJD0J1q9tPLRPSMWDZEzoRq408b9ah8ka8f
ONOE1Zpd6k9mRG1f3hw9rU
+SA3eyay72KNmLr7jH4rKnDNGQs0PDIo7+hHZrYNkd3SQfQBTJy0Z/TR4VCnPXjID8
+P+Ml4ia+O4+0Y491NzSztLM605mai+AtPMrCb/WEsC/
Vv7mBq2TWJemcakUP5U4W3wLDUpz1kEVlf98cX3Pc9VA
VZp+sF4vGLaAKp+e9/mIAbFLPB01IOlzlpZJikpliPkMV6NNzPSSPLaSf5Rhi72XLOo
+f16i+mXOgTJYgC9snwnm
2/FyDu32MuMl9rcDjzjIShQDpmPF78oOeEzMSCVsMIpo0EK+qwS1QOySDZySUVpS
+gqMiacgDsdTsGBvk+MUiJeI
ohTZd3HMa0UwUW/eGo82d+t/9cEHFfwgv8WMuGJJd4/oPlgttNz/caRb6ih5VJ1vGY7uf0/
jngzF+ZZb1l5JSRez
Sv/vTk2iiOWwyjw7Y8pDMNhqRL
+zphCU3OH7znu64GXr1yRYOkIgXpfO2hET1ztm37CFEy5zHH5YfpogVPqKpF5p
XyVIMNnA9ATJ2Qjf9d0nyJZjVo7xHh
+gFTKmxMErUnXqxdL68PWQoRxSMd0J87L73aXJ1u0IovuqZbYu
---------------------------------------------------------------------------------------
i got some help from some friends here so i could get alice private
and public key while bob's keys are still undiscovered ..!!!!!!
A private key is a publically available key as long as the Alice
initiation demands a verification of autheticity. A communication
channel coverty listened in on will record the authentication.
Assume the first message is a prior authentication message.
65537
Allowing Alice a key. The channel key is only inferred. A good
message authentication has a set of authentication prior messages, one
for each channel attempt.
So the key is NOT in record on the channel!
This is Alices public authentication key.
376781096648655171476075046480384036003069767135878367046892404899787
642486409
Alice can infer the channel key for the returned reply.
Alice(new channel key) = Function(65537)(Alice Private key)
Ask the question backwards now. How to allow the hidden channel key
without the prior message?
And it is impossible.
Except
Function(Alice channel)(Alice private key) = Function(Bob channel)(Bob
private key)
Making the two only need to imply the usage of the ALice channel key
as opposed to the bob channel key!
So to discover all keys is impossible from the system utilized.
A crack of the system then becomes a thing of cracking the Function
and NOT the Authentication design. It is tthe correct design. |
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| Mido... |
| Posted: Sat Jul 19, 2008 8:28 pm |
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Guest
|
On 9 Jul., 14:03, Douglas Eagleson <eaglesondoug... at (no spam) yahoo.com> wrote:
Quote: On Jul 8, 12:56 pm, Mido <mideast3... at (no spam) gmail.com> wrote:
Hi,
well it's a quizz that i had in some security course in uni but i
couldnt and no one could help solving it so far!!
and here is the quizz
Alice >> Bob:
65537,376781096648655171476075046480384036003069767135878367046892404899787642486409
Bob >> Alice:
282833517591435239342270053773279218579315796727277426826963893552262154129057
038465481487634624354845048059184314627639662982706432909184536115489229069975
171303235680267287580845213988591987016737683250608291454783603000401455241565
Alice >> Bob:
hOt7FrXiOxhE9u8D0MzORMkzya6OxejiD0zM9EMav57s8jzYrECA1+9sop4XtY9LlXWi3KpAF49+OIFisSIW4HDI
Pkbt1vg/
0pL2DCAkHlRiSVUwzQnJ8LkomsiDg6ZxYklVMM0JyfC5KJrIg4OmcWJJVTDNCcnwuSiayIODpnFiSVUw
zQnJ8LkomsiDg6Zx8C3K9jXtqcuyerT8rdX7ULUFA3FfGRY9gNKJtF2G6s44r0dfp0lh6I5pvLUeoRmXDUNf4O3k
Cc/
B9vbfgluoY2W5T6F8uEewS66adCwS8R8Pw55pUODH5QEu05qr1IJD0J1q9tPLRPSMWDZEzoRq408b9ah8ka8f
ONOE1Zpd6k9mRG1f3hw9rU
+SA3eyay72KNmLr7jH4rKnDNGQs0PDIo7+hHZrYNkd3SQfQBTJy0Z/TR4VCnPXjID8
+P+Ml4ia+O4+0Y491NzSztLM605mai+AtPMrCb/WEsC/
Vv7mBq2TWJemcakUP5U4W3wLDUpz1kEVlf98cX3Pc9VA
VZp+sF4vGLaAKp+e9/mIAbFLPB01IOlzlpZJikpliPkMV6NNzPSSPLaSf5Rhi72XLOo
+f16i+mXOgTJYgC9snwnm
2/FyDu32MuMl9rcDjzjIShQDpmPF78oOeEzMSCVsMIpo0EK+qwS1QOySDZySUVpS
+gqMiacgDsdTsGBvk+MUiJeI
ohTZd3HMa0UwUW/eGo82d+t/9cEHFfwgv8WMuGJJd4/oPlgttNz/caRb6ih5VJ1vGY7uf0/
jngzF+ZZb1l5JSRez
Sv/vTk2iiOWwyjw7Y8pDMNhqRL
+zphCU3OH7znu64GXr1yRYOkIgXpfO2hET1ztm37CFEy5zHH5YfpogVPqKpF5p
XyVIMNnA9ATJ2Qjf9d0nyJZjVo7xHh
+gFTKmxMErUnXqxdL68PWQoRxSMd0J87L73aXJ1u0IovuqZbYu
---------------------------------------------------------------------------------------
i got some help from some friends here so i could get alice private
and public key while bob's keys are still undiscovered ..!!!!!!
A private key is a publically available key as long as the Alice
initiation demands a verification of autheticity. A communication
channel coverty listened in on will record the authentication.
Assume the first message is a prior authentication message.
65537
Allowing Alice a key. The channel key is only inferred. A good
message authentication has a set of authentication prior messages, one
for each channel attempt.
So the key is NOT in record on the channel!
This is Alices public authentication key.
376781096648655171476075046480384036003069767135878367046892404899787
642486409
Alice can infer the channel key for the returned reply.
Alice(new channel key) = Function(65537)(Alice Private key)
Ask the question backwards now. How to allow the hidden channel key
without the prior message?
And it is impossible.
Except
Function(Alice channel)(Alice private key) = Function(Bob channel)(Bob
private key)
Making the two only need to imply the usage of the ALice channel key
as opposed to the bob channel key!
So to discover all keys is impossible from the system utilized.
A crack of the system then becomes a thing of cracking the Function
and NOT the Authentication design. It is tthe correct design.
well Douglas not really correct what you explained cause i had reached
the full decryption of ther quizz and here is what i had done as to
solve it
first you factorise the larg number which is shown in the second part
of Alice's first message then to use the parameters p and q as to get
the rest of the RSA parameters needed to decrypt whatever the other
part sends
now we decrypt using the public key of alice that we already got out
of her first message to decrypt Bob message ... after that we get some
info out of his message which was an AES key .. now we focus on the
second message of Alice .. we do some Base64 decryption then we start
decrypting what we got using a block based decryption method which
requires doing the AES decryption block by block.. in the end you
would get the fully decrypted text which is
Congratulations, you managed to break the final challenge of this
lecture!!
==========================================================================With this challenge you could see, that it is possible to break a
cryptosystem even if parts of it are considered unbreakable. Here we
used
the fact, that the RSA modulus was choosen too small, and it was
possible
to factorize it. The two factors used are 118 and 140 Bit, which is
way to
small for today's standards. On the other side, breaking the 128 Bit
key of
AES would not have been possible. Hence, a cryptosystem always breaks
at
it's weakest point similar to a real world chain.
Your codeword for this challenge is FACTORIZATION! |
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| Douglas Eagleson... |
| Posted: Sun Jul 20, 2008 4:25 am |
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Guest
|
On Jul 19, 11:28 pm, Mido <mideast3... at (no spam) gmail.com> wrote:
Quote: On 9 Jul., 14:03, Douglas Eagleson <eaglesondoug... at (no spam) yahoo.com> wrote:
On Jul 8, 12:56 pm, Mido <mideast3... at (no spam) gmail.com> wrote:
Hi,
well it's a quizz that i had in some security course in uni but i
couldnt and no one could help solving it so far!!
and here is the quizz
Alice >> Bob:
65537,376781096648655171476075046480384036003069767135878367046892404899787642486409
Bob >> Alice:
282833517591435239342270053773279218579315796727277426826963893552262154129057
038465481487634624354845048059184314627639662982706432909184536115489229069975
171303235680267287580845213988591987016737683250608291454783603000401455241565
Alice >> Bob:
hOt7FrXiOxhE9u8D0MzORMkzya6OxejiD0zM9EMav57s8jzYrECA1+9sop4XtY9LlXWi3KpAF49+OIFisSIW4HDI
Pkbt1vg/
0pL2DCAkHlRiSVUwzQnJ8LkomsiDg6ZxYklVMM0JyfC5KJrIg4OmcWJJVTDNCcnwuSiayIODpnFiSVUw
zQnJ8LkomsiDg6Zx8C3K9jXtqcuyerT8rdX7ULUFA3FfGRY9gNKJtF2G6s44r0dfp0lh6I5pvLUeoRmXDUNf4O3k
Cc/
B9vbfgluoY2W5T6F8uEewS66adCwS8R8Pw55pUODH5QEu05qr1IJD0J1q9tPLRPSMWDZEzoRq408b9ah8ka8f
ONOE1Zpd6k9mRG1f3hw9rU
+SA3eyay72KNmLr7jH4rKnDNGQs0PDIo7+hHZrYNkd3SQfQBTJy0Z/TR4VCnPXjID8
+P+Ml4ia+O4+0Y491NzSztLM605mai+AtPMrCb/WEsC/
Vv7mBq2TWJemcakUP5U4W3wLDUpz1kEVlf98cX3Pc9VA
VZp+sF4vGLaAKp+e9/mIAbFLPB01IOlzlpZJikpliPkMV6NNzPSSPLaSf5Rhi72XLOo
+f16i+mXOgTJYgC9snwnm
2/FyDu32MuMl9rcDjzjIShQDpmPF78oOeEzMSCVsMIpo0EK+qwS1QOySDZySUVpS
+gqMiacgDsdTsGBvk+MUiJeI
ohTZd3HMa0UwUW/eGo82d+t/9cEHFfwgv8WMuGJJd4/oPlgttNz/caRb6ih5VJ1vGY7uf0/
jngzF+ZZb1l5JSRez
Sv/vTk2iiOWwyjw7Y8pDMNhqRL
+zphCU3OH7znu64GXr1yRYOkIgXpfO2hET1ztm37CFEy5zHH5YfpogVPqKpF5p
XyVIMNnA9ATJ2Qjf9d0nyJZjVo7xHh
+gFTKmxMErUnXqxdL68PWQoRxSMd0J87L73aXJ1u0IovuqZbYu
---------------------------------------------------------------------------------------
i got some help from some friends here so i could get alice private
and public key while bob's keys are still undiscovered ..!!!!!!
A private key is a publically available key as long as the Alice
initiation demands a verification of autheticity. A communication
channel coverty listened in on will record the authentication.
Assume the first message is a prior authentication message.
65537
Allowing Alice a key. The channel key is only inferred. A good
message authentication has a set of authentication prior messages, one
for each channel attempt.
So the key is NOT in record on the channel!
This is Alices public authentication key.
376781096648655171476075046480384036003069767135878367046892404899787
642486409
Alice can infer the channel key for the returned reply.
Alice(new channel key) = Function(65537)(Alice Private key)
Ask the question backwards now. How to allow the hidden channel key
without the prior message?
And it is impossible.
Except
Function(Alice channel)(Alice private key) = Function(Bob channel)(Bob
private key)
Making the two only need to imply the usage of the ALice channel key
as opposed to the bob channel key!
So to discover all keys is impossible from the system utilized.
A crack of the system then becomes a thing of cracking the Function
and NOT the Authentication design. It is tthe correct design.
well Douglas not really correct what you explained cause i had reached
the full decryption of ther quizz and here is what i had done as to
solve it
first you factorise the larg number which is shown in the second part
of Alice's first message then to use the parameters p and q as to get
the rest of the RSA parameters needed to decrypt whatever the other
part sends
now we decrypt using the public key of alice that we already got out
of her first message to decrypt Bob message ... after that we get some
info out of his message which was an AES key .. now we focus on the
second message of Alice .. we do some Base64 decryption then we start
decrypting what we got using a block based decryption method which
requires doing the AES decryption block by block.. in the end you
would get the fully decrypted text which is
Congratulations, you managed to break the final challenge of this
lecture!!
==========================================================================> With this challenge you could see, that it is possible to break a
cryptosystem even if parts of it are considered unbreakable. Here we
used
the fact, that the RSA modulus was choosen too small, and it was
possible
to factorize it. The two factors used are 118 and 140 Bit, which is
way to
small for today's standards. On the other side, breaking the 128 Bit
key of
AES would not have been possible. Hence, a cryptosystem always breaks
at
it's weakest point similar to a real world chain.
Your codeword for this challenge is FACTORIZATION!- Hide quoted text -
- Show quoted text -
You are cracking the key a hidden key. A message as alices first
message was the text to cause the exact message key.
You broke the system by cracking. A good method uses hard method to
crack on both authentication schemes.
Good job. |
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