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Apr
18
comment What are application of Cryptography in Algebraic Topology
possible duplicate of What are the links between Cryptography and Algebraic Topology?
Apr
18
comment Is chaotic encryption secure?
I located a review with a section about that chapter. It really is an overview, and totally non-committing.
Apr
17
comment Is chaotic encryption secure?
Count me as fully open to the idea that a chaos-based cryptosystem can be made secure, but highly skeptical that it has any advantage over established cryptosystems.
Apr
17
comment What are application of Cryptography in Algebraic Topology
It is usually mathematic fields that find application in cryptography, rather than the other way around (as asked). Cryptography in turn finds application in even more applied fields, like payment.
Apr
17
comment Key space vs Cardinality of 1024-bit RSA
To avoid duplicate moduli we want $p<q$, that about halves the cardinality. And then, what about $e$ ? Setting a fixed $e=3$ reduces the cardinality by a factor of about $4/9$. If $e$ is allowed to vary, and we defined an RSA key as $(p\cdot q,e)$, our cardinality increases (and we should account for equivalent $e$ if very large $e$ are allowed). And then, many practical RSA key generation algorithms only generate primes of a certain form (like, such that $p-1$ and $p+1$ each have a known prime factor of a fixed bit size) and that reduces the cardinality of what they could generate.
Apr
15
comment Difference between IPSEC SA and CHILD SA
This is off-topic, because that's very specific to a particular security product, rather than cryptosystem. I suggest migration to security.stackexchange.com
Apr
15
comment Asymmetric encryption that is secure for (almost) any foreseeable future
It is not stated to what certainty degree it is required that the scheme remains secure after 1000 years, and that's an important parameter. It is much easier to predict very long term things with 30% chances to be wrong, rather than with 0.03% chances (a residual risk level often accepted in security, about that of having one's Smart Card pin guessed). One reason many key length estimates in the distant future are so conservative is that they are made with the intend to only err on the safe side.
Apr
15
comment Factoring two RSA modulus with known $|p_1 - p_2| < \ell $
I fail to see how the examination of the bits of the ratio$N_1\over N_2$ reveals information on $a$ (as stated in the but-last paragraph of the current answer). As a minor aside, $|p_1-p_2|\le2^s$ is not quite a sufficient condition to insure that $\lfloor p_1/2^s\rfloor=\lfloor p_2/2^s\rfloor$, thus existence of $a$. That part is easily fixable: with $s=\lceil\log_2\ell\rceil+4$, it is quite likely $a$ exists.
Apr
15
comment Factoring two RSA modulus with known $|p_1 - p_2| < \ell $
@mikeazo: in the present question $0<|p_1-p_2|<\ell$, in the other question that you linked (transposing the notation to match that in the present question), we have $|p_1-q_1|<\ell$. $\;$ I have not understood the proposed attack, and fail to see one. $\;$ I second Lisbeth's approach to first try to solve the problem with $p_1-p_2=2$.
Apr
14
comment Meaning of Signature hash algorithm field in certificate
@Dandan: only $Pub_B$ is in the certificate that we are talking about in the question and answer. $Pub_A$ is the public key of the certification authority, is typically designated (not contained) in the certificate's data, and is known and trusted either because it is built in the software that verifies certificates, or because it is introduced by another certificate including a signature verified by yet another known and trusted public key. Sometime $Pub_A=Pub_B$, this is a self-signed certificate, and we can trust these only if they are known to come from a trusted source.
Apr
14
comment RFID Protocol Cryptanalysis
Think about it again: with the protocol as described, some message loss can turn the step "they both add $r_1$ to the key set" into something where one of TAG or READER did this, and the other did not.
Apr
14
comment RFID Protocol Cryptanalysis
In RFID, the TAG goes from a READER to another; as far as I understand the scheme outlined, the various readers need to know the current sate of a given TAG, by communicating between each others in some way, which is not something to lightly consider for granted in the physical world. $\;$ Independently, it is frequent that a message is lost between TAG and READER (in either direction), and the protocol outlined does not seem to account for that inescapable fact. $\;$ So before asking if it's secure (and defining the meaning of that): does it even work in the absence of adversary?
Apr
14
comment Benefit of using random key in Shamir's Secret Sharing
I would be very surprised that the shares in the first example decode to "Hello" using any natural (nothing-up-my-sleeves) implementation of Shamir secret sharing. $\;$ Perhaps you are confusing key (usually understood as the secret value of a share, or shares, or the secret shared), and index (the identifier of a share, usually public), and really wanting to ask if there is benefit in using random index in Shamir secret sharing? In any case, it would help if you defined what benefit you expect; can't be about secrecy of the shared secret, Shamir secret sharing provably insures this.
Apr
13
comment What are the difference between cryptographic primitives and encryption primitives?
@Stephen Touset: Perhaps: Diffusion and confusion are desirable (and necessary) properties of internals of block ciphers. For a complete cipher as a whole, full diffusion is rare (no standard operating mode offers full diffusion of plaintext to ciphertext). $\;$ Glad to see we independently came with properties.
Apr
13
comment What are the difference between cryptographic primitives and encryption primitives?
I would not say confusion and diffusion are primitives; they sound to me as properties of primitives (but I'm not a native English speaker). Also, these terms are a little dated, and (especially confusion) seldom precisely defined. Shifting is ambiguous (often it is to be understood as rotating), and substitution has two meanings (some are a mapping, others not). $\;$ So all in all I see no way to precisely answer.
Apr
13
comment How does the Blowfish algorithm key initialization work
@Ben: unfortunately this answer is not enough to fully cover the variations found in the field; see new Final Caution!
Apr
12
comment Using similar passwords and salts for PBKDF2
Also: consider Scrypt rather than PBKDF2; it gives a significantly better protection against ASIC-based brute force attacks for the same cost of legitimate use.
Apr
12
comment AES-XTS: find key from ciphertext and plaintext
All known ways to obtain the key require more input; like, the power consumption over time of the device that performed the computation.
Apr
11
comment OTP - Reusing key IS SECURE! PROVED!
By XORing the 4 formulas, it comes that independent of keys and IVs, $character_4=$ $character_1⊕character_2⊕character_3⊕cipher_1⊕cipher_2⊕cipher_3⊕cipher_4$.
Apr
11
comment OTP - Reusing key IS SECURE! PROVED!
This "proof" is not even wrong. Also, even if "IVs" are secret, character 4 is trivialy found from ciphertexts and the other three characters.