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seen Jan 10 '13 at 13:25

Oct
18
revised Traditional DES scheme in Unix crypt function
added 90 characters in body
Oct
18
answered Traditional DES scheme in Unix crypt function
Oct
18
comment Hill Cipher known plaintext attack
It is interesting to see that your update expands the steps described in my comment that you doubt above. (We're not unlucky here since the system---leading to the discovery of the first row of the decryption matrix---has exactly two solutions.) btw: +1 for the clean description of the standard key recovery strategy (although you could have avoided the cumbersome indexing scheme: it's compact for you to write but a pain to read)
Oct
17
comment Is there a symmetric-key cryptography based on key establishment techniques?
Why shouldn't the nonce be sent in the clear? They do not need to remain secret, the pre-shared key serves this purpose already.
Oct
17
comment Is there a symmetric-key cryptography based on key establishment techniques?
@Vucamille: And on top of this, even if the pre-shared key has a good entropy, the key tends to weaken with use; this is the reason why session keys are used instead and changed frequently; hence, there is a need for key derivation based on pre-shared keys; one might to call this key agreement since other infos such as nonces are also introduced...
Oct
17
comment Hill Cipher known plaintext attack
in general no, but there must be a way to solve this, and with an exhaustive search in about 8, not $26^2$; I don't believe redundancy can be exploited here as the text is very short, but if one knows the language, since every third letter of the plaintext is known, one might guess some additional letters; however, redundancy in the plaintext is not the only information that can be exploited: ciphertext structure can as well; for instance I believe "iae" encrypts to "MOE" but I derived this from the ciphertext's structure; (caveat: I did not find the key, arithmetic in $Z_{26}$ is a pain ;p)
Oct
17
comment Hill Cipher known plaintext attack
@ecem: try to find the decryption matrix. You have enough information to compute it entirely. (Start by recovering three of its entries.)
Oct
17
comment Hill Cipher known plaintext attack
What are the second value and the third value of the ciphertext of length 12? (Or maybe you can post all of the values? We won't give the solution, but hint towards the method.)
Oct
17
comment Is there a symmetric-key cryptography based on key establishment techniques?
I assume you're mislead by the use of the wording "key exchange", but I refer you to the wording of the question, which is about "key establishement" or in other words, key agreement. Sashank specified that a preshared secret (PSK) exists already between the two parties so there is no problem with exchanging the remaining information on the public channel (nonces, identity based information, etc.). For information, this is also how things work in wireless pairings...
Oct
16
revised Hill Cipher known plaintext attack
added 70 characters in body
Oct
16
revised Hill Cipher known plaintext attack
added 722 characters in body
Oct
16
answered Hill Cipher known plaintext attack
Oct
16
answered Is there a symmetric-key cryptography based on key establishment techniques?
Oct
16
awarded  Excavator
Oct
16
revised Proving knowledge of a preimage of a hash without disclosing it?
fixed typo in title
Oct
16
suggested suggested edit on Proving knowledge of a preimage of a hash without disclosing it?
Oct
16
revised Key Scheduling of International Data Encryption Algorithm (IDEA)
added 4 characters in body
Oct
16
suggested suggested edit on Are there secure stream ciphers that cannot be parallelized?
Oct
16
answered Key Scheduling of International Data Encryption Algorithm (IDEA)
Oct
15
revised Ways to protect flash player against MITM diffie hellman
slight change of wording