What mathematical fields of knowledge would be required in order to get a good understanding of encryption algorithms? Is it basic algebra, or is there a "higher education" mathematical field dedicated to encryption? I know there is the cryptography field, but what is the subset of knowledge requ...

Consider this command on a trusted computer: result = function(public data, secret data) or shorter: r = f(p,s). How could a function on an untrusted computer produce the same result without the secret data being available to the untrusted computer? Abstract example: r = f(p, s) = f'(p1, p2, ...

Taken from http://en.wikipedia.org/wiki/Homomorphic_encryption, $\mathcal{E}(x_1) \cdot \mathcal{E}(x_2) = x_1^e x_2^e$ $\bmod\; m = (x_1x_2)^e \;$ $\bmod\; m = \mathcal{E}(x_1 \cdot x_2)$ What is the superscript $^e$ representing in the first expression, and how do we get from the second line...

I have recently started looking into creating secure, while not validating against an external server, software product keys. The idea I have had is to create a key consisting of two parts firstly a section that contains some (but not all) details of the user; for example name, customer ID and m...

The security of RSA is based on the integer factorization problem, which is a very well defined and understood mathematical problem. This problem must be solved in order to fundamentally break RSA. What about AES (and others based on the same idea)? Why is it difficult to break? Is there any ma...

I am designing a library that supports encrypting some in-memory data using AES in CBC mode. Now I need a padding but it seemed to me that Apple's CommonCrypto library and OpenSSL have different padding schemes but I want to retain interoperability even when mixing CommonCrypto implementation and...

I've read a few papers recently that used a notion of security called "indistinguishability from random bits/strings" under chosen plaintext attack, also called IND\$-CPA. See e.g. http://pdf.aminer.org/000/217/279/nonce_based_symmetric_encryption.pdf. The authenticated encryption mode "OCB" is...

I was looking all over the Internet list of ALL existing symmetric and asymmetric ciphers. I know that there's, for example, AES, DES, Blowfish, DSA. But how about more? Where to find such list?

So, as we all know, Dual_EC_DRBG contains an NSA back door. At this point, there is no reason to call it a "potential" or even an "alleged" back door; the presence is obvious even to the NY Times. As we also know, RSA BSAFE has been using Dual_EC_DRBG by default, with a justification so stupid i...

Following are steps to conduct Chosen Plaintext Attack (CPA) indistinguishibility experiment $PrivK_\mathcal{A,E}^{eav}(n)$. $\mathcal{A}$ is the adversary $\mathcal{E}$ is the encryption scheme (Gen, Enc, Dec), $n$ is the length of the input. a secret key SK is generated using Gen($1^n)$ $\...

On pg. 11 Definition 2 it outlines the following steps (PK,SK) public key and secret key are generated by defender using Gen($1^n$) adversary $A1$ generates $m_0$ and $m_1$ and a $state$ using PK defender randomly selects $b$ and encrypts $m_b$ invoking $ENC_{PK}(m_b) = y$, and given to $A2$. u...

A recent blog post from Ivan Ristić (expert extraordinaire on all things SSL) says: all major browsers are susceptible to protocol downgrade attacks; an active MITM can simulate failure conditions and force all browsers to back off from attempting to negotiate TLS 1.2, making them fall back a...

The wiki defines the decisional Diffie–Hellman assumption as follows: Decisional Diffie–Hellman assumption Consider a (multiplicative) cyclic group $G$ of order $q$, and with generator $g$. The DDH assumption states that, given $g^a$ and $g^b$ for uniformly and independently chosen $a$,$b$ $\in...

I have a Raspberry Pi single-board computer that happened to have an hardware true random number generator, based on some quantum effects on the processor silicon, baked into its BCM2835 chip and I can pump its randomness by dumping bits from /dev/hwrng device in Raspbian, its Debian-based Linux ...

I'm working to decrypt the following text encrypted with a mono alphabetic shift cipher. JGRMQOYGHMVBJWRWQFPWHGFFDQGFPFZRKBEEBJIZQQOCIBZKLFAFGQVFZFWWE OGWOPFGFHWOLPHLRLOLFDMFGQWBLWBWQOLKFWBYLBLYLFSFLJGRMQBOLWJVFP FWQVHQWFFPQOQVFPQOCFPOGFWFJIGFQVHLHLROQVFGWJVFPFOLFHGQVQVFILE OGQILHQFQGIQVVOSFA...

I've been reading the wikipedia page, trying to get a better understanding of how to produce a collision. http://en.wikipedia.org/wiki/MD5#Collision_vulnerabilities The wikipedia page above states: "two colliding files is a template file with a 128-byte block of data, aligned on a 64-byte bound...

I heard that key/IV pairs must not be reused in AES-CTR, or when using any stream cipher for that matter. Yet the attacks described do not seem to apply to AES-CBC. Is reusing the same key several times dangerous in AES-CBC mode? Does the use of a random IV preclude all possible attacks in such...

I've read that the Whirlpool hash function can produce footprints that could be used as a pseudorandom generator. Is it "OK" to use it to encrypt some data using something like the following? EncryptedData = Concat(DataBlock XOR Whirlpool(DataBlock + SecretKey))

Can someone clarify what is meant by the terms cryptosystem bandwidth and block size for public key cryptosystems; The context is the Paillier cryptosystem and its Damgard-Jurik generalisation. My intuition is that they refer to the modulus. Since the modulus is $n^2$ and $n^s$ respectively does ...

I'd like to extract the entropy of data without injecting "pseudo" entropy (eg, by encrypting with AES-CTR). For example, let's say I have a series of bytes, but only the low bit is changing (or something is changing that I'm not aware of beforehand). Is there a known way to extract the random p...

I want to know that any other algo which is better than RSA and rabin(asymmetric).

We all love Cryptography Stack Exchange, but there is a whole world of people out there who need answers to their questions and don't even know that this site exists. When they arrive from Google, what will their first impression be? Let's try to look at this site through the eyes of someone who'...

Our cryptography lounge has been frozen due to inactivity. I feel it is important it be revived, but after some searching on MSO it appears only moderators can unfreeze rooms. Can we reopen the room?

It's rather kind of lame questions, and I can't find good and clear explanation: In which step of Rijandel S-box is generated? Does the S-box is re-used in every round of cipher or is generated in every iteration? In coursarea movie where is explanation of AES: https://class.coursera.org/crypto...

Please forgive this beginner’s question. I have not been able to find an answer online or in the literature, searching under all the search terms I can think of. Nevertheless I suspect the answer is well-known, hence I am asking here. Suppose we define a PRG as the xor of two LCGs modulo a 64-bi...

I am running into a particular problem and I do not know which way to proceed. Here is what is going on. I have the need to represent around 98 million radio configurations each of 32 bits (32 channels each being on/off). I am told that with Paillier implemented at 1024 bit security parameter,...

Does anyone know if OpenSSL's default CSPRNG is Dual_EC_DRBG or not? Their wiki is not very clear Related to the first question, does anyone have any experience with OpenSSL on Mac changing the default CSPRNG? It is quite interesting that there is not much info anywhere on the Internet related...

This is a hypothetical question and I only have a basic understanding of Cryptography. If one were to follow the very best cryptographic practices for storing passwords, could it ever be possible to publish literally all information (the usernames, the hashes, the salts, the algorithms used) and...

First off, I'm extremely sorry if this comes off as a "homework dump", but to clarify, it isn't. I don't want the answer, I want to know how to get to the answer. My cryptography professor gave us an assignment to do, and without explaining this concept, he believes we all understand how to do it...