AES (Advanced Encryption Standard) is a symmetrical block-cipher algorithm with a 128-bit block size, and key sizes of 128, 192 or 256 bits.

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Can I use the output from a DRBG directly as K for AES, or do I need to use a key generator algorithm?

NIST has 3 validated "Recommendation for Random Number Generation Using Deterministic Random Bit Generators" (DRBG's) that are based on NIST SP 800-90A: Hash_DRBG (based on hash functions) ...
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632 views

Why is AES unbreakable?

Why is it said that AES is unbreakable? Brute force attacks would take years to crack it, so is it possible to crack it if the computational speed of machines increase in the following decade?
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416 views

Is splitting AES ecrypted data safe?

Say I have a key, an iv and an AES/GCM/NoPadding encoded string and I want to split this information between three people such that only jointly can they reveal the ...
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Generate fixed length cipher text from arbitrary length plaintext

Using an encryption algorithm like AES, is it possible to generate a fixed length cipher text no matter how long the plain text becomes?
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AES key equal to IV (CBC mode)

Application uses AES in CBC mode with 128 bit key. In this implementation key is always same and is equal to IV. Can attacker get the key or decrypt data? If he knows: First and second blocks of ...
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127 views

Algorithm to transform plaintext to a key of desired keysize, when using input plaintext as key for FPE?

Using a format preserving encryption scheme that uses AES internally as its block cipher, for a plaintext that I encrypt I want to use that input plaintext as the key. However using AES-128, my ...
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179 views

Is there a way to encrypt an integer within an arbitrary range?

I need an algorithm that can take an integer, an arbitrary range, a key of 16/24/32 bytes, and an initialization vector of 16 bytes(ideally), and return an integer in the same range. My latest attempt ...
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121 views

How much pre-hashing a password increase security against brute force attack?

I am wondering how much hashing a password used as key for a symmetric key algorithm helps preventing brute force attack on crypted text. Let's assume I want to crypt text A using key B using AES-...
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185 views

Can AES be considered as Perfectly Secure?

I am studying about the AES encryption standard, and as I know from the theory there is no known weaknesses today about this block-cipher. I would like to find out or at least to understand what "...
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What is more secure, a ciphertext encrypted with AES-256 or encrypted with 3 different AES-128 keys?

Or better yet, is encrypting a block with 2 AES-128 keys just as secure as encrypting a block with 1 AES-256 key? By the way, I've only recently been learning cryptography stuff; I've made working ...
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825 views

Encrypting firmware with AES and no IV [closed]

I have an embedded device with a AES CBC engine on it that is used to ensure the integrity of the firmware. I know that CBC mode requires unique IVs to be any good, but I'm unsure if it makes a large ...
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AES Algorithm processing time in Arduino vs Raspberry Pi

The Arduino employs an 8-bit ATmega series microcontroller whereas the Raspberry Pi is based around a 32-bit ARM processor, and the Arduino is typically clocked at between 8-16MHz and with 2-8kB of ...
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HMAC vs Encrypted Hash

What is best to use (for message integrity) between… AES(Data) + HMAC(Data) AES(Data + HMAC(Data)) AES(Data + Hash(Data)) …and why?
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382 views

How to verify a shared secret using only AES?

I have two devices that need to verify that they both are in possesion of the same secret key. One of the devices is a very limited embedded device that only has AES128 available, no SHA or other hash ...
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1k views

AES-CMAC passes every test except two

i wrote this code: ...
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AES encryption for pairwise identifiers

I'd like to map a random ID of 16 bytes (sourceID) to another random ID of 16 bytes (targetID). The operation should: only be reversible by me be deterministic There are about 1 million source ...
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113 views

Is super encryption (aka “multiple encryption”) always good?

I'm trying to use super encryption (also known as “multiple encryption”) with AES in CFB mode with IV and password salting and AES in CTR mode both without padding. I first use AES CFB and then AES in ...
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167 views

Implement AES with 16 bit block size?

Can we implement AES with 16 bit block size ?if so what are its advantages and disadvantages?Is there any rule AES has to be implemented with 128,192,256 ?Can we use AES for odd number of bits(17,33,...
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231 views

Ensuring integrity and confidentiality together with symmetric encryption

I've been required to answer a question: As usually, we have Alice and Bob. Suppose Alice wants to send a file F to Bob, ensuring integrity and confidentiality. They share a symmetryc key $K_{...
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223 views

CLEFIA vs AES 128-bit

I am running a comparison between CLEFIA(Lightweight cipher from Sony Corporation which is a standard now http://www.sony.net/Products/cryptography/clefia/standard/index.html) and AES 128-bit. The ...
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277 views

Is the output of AES-CBC + MAC the same size as the input?

I use AES-CBC and HMAC-SHA256 to encrypt a text file. Will the output be larger in size than the input or will it be the same size? Is it more secure secure if the size of the output is larger?
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Adding an IV to an AES implementation

I have an embedded project that requires AES, I seem to have found an AES implementation that fits the bill here: http://www.literatecode.com/aes256, but it does not include an IV. Are there any ...
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Key cracking: Prefer many small texts over one large text?

If an attackers sets out to crack the symmetric key of e.g. AES-CTR, would they prefer to have access to many small cryptotexts or one large cryptotext? I.e. is it more interesting for the attacker to ...
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207 views

Is CTS necessary on a AES-CBC DRBG?

As I understand it, CTS pads the last block and swaps it with the second last to compensate for a partial block of data. I have written a DRBG (Deterministic Random Bit Generator) using AES-CBC that ...
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113 views

Prefixing data before encryption for passphrase confirmation?

I'm encrypting data with AES, using CryptoJS. CryptoJS returns an empty string in case the data couldn't be encrypted with the given passphrase. I'm not sure if this is intended, or happens in all ...
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Is the salt value a secret or can it be stored in cleartext just like the IV? [duplicate]

From Wikipedia I read that the IV is used to randomise the mapping of cleartext to cipher text and that the IV is usually stored (in cleartext) together with the encrypted record. (http://en.wikipedia....
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Is it worth applying a MAC on data in a HSM?

I'm building a basic HSM out of an Arduino, and am using the following scheme to store data: Master symmetric key $k_m$ stored in firmware (secure bit set to prevent trivial extraction). Secondary ...
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636 views

Partial decryption of large file in AES-GCM (or other modes)?

Lets assume a 4gig file that is internally made of 1 million pages of 4k bytes each (page). the file was originally AES-GCM encrypted these pages (or entire file) lives across the internet i.e. ...
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Removing Padded Value in Decrypted Message

How to remove padded value in Decrypted Message? I am using AES Algorithm. Let's take this as the decrypted message: "abcdefghijklmn " There is a 2 space in ...
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304 views

Factoring a polynomial over a GF [closed]

I have the following question: What polynomial, when factored over the field $GF (2^8)$ based on the irreducible polynomial that is used in Rijndael, will factor into all the polynomials in the ...
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62 views

How is decryption done in AES CTR mode?

Since AES CTR mode uses a unique IV and counter to produce the key to XOR with the plain text to get the ciphertext, the question is so as to how decryption is done. Since AES CTR produces a ...
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73 views

SHA256(RsaPrivateKey) == AES key?

I have an RSA private key (more specifically, an SSH key in Putty format, 4096bit) and want to use its SHA256 hash as an AES256 key, instead of using an independent newly generated AES key. Are ...
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53 views

Disk encryption using AES-CBC: is reliance on previous block data a downside?

I have seen drives that boast that they use AES with CBC mode, which doesn't really make sense in my opinion, sure it's more secure than ECB (but actually, leaving security aside, ECB is better suited ...
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HMAC-SHA1 vs. AES

This might be a very silly question, but I am a total novice in encryption. I don't know where to start searching for an answer to this problem. I am building applications using a proprietary ...
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Is it safe to use AES-CBC like this?

Is it safe to generate the IV for AES-CBC as the following? It's like the real IV is all zeros. The first block of data will be a low-entropy but unique data. Once the first block is encrypted, the ...
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126 views

AES-256 mode with per-block-key being a SHA-256 of SHA-256 of secret key, random public salt and block number. What's amiss?

Please criticize the (homebrew?) mode described below; to point out a single major defect/uncertainty or the link to (the analysis of) an equivalent construction is quite enough. Assume the ...
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680 views

Precisely how does CBC mode use the initialization vector? [duplicate]

As I understand it, AES in CBC mode does an XOR of the 128-bit initialization vector and the first 128 bits of plain text. Is this correct? I am using the PHP 5.3 openssl extension in aes-256-cbc ...
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Padding size with a CBC Block cipher in TLS

I'm currently looking at an encrypted Client Finished message in Wireshark from a TLS session. The cipher suite that was agreed on in previous messages was ...
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147 views

Is it OK to encode data using key equal to data

For some project, I need to store some short string in encrypted form. It would be ideal for the current purposes to encrypt it using itself. ...
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Is a padding oracle attack possible if data is only encrypted internally on a server (e.g. for storage)?

I read something about the padding oracle attack when analysing the use of an AES-encryption of data in a database and was "scared" it could be a serious issue. But after investigating a bit further, ...
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559 views

Why don't PyCrypto and M2Crypto produce the same result as OpenSSL here (AES-128 ECB)

If I run the following, for openSSL: echo -n "0123456789abcdef0123456789abcdef" | openssl aes-128-ecb -nosalt -nopad | xxd and enter the key "YELLOW SUBMARINE", ...
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78 views

Hardness proof?

I am little curious about how do we calculate hardness proof of any cryptography algorithm? Also where can I find hardness proof for AES and AES-CBC ?
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where to keep the AES keystream?

I am trying to implement an AES encryption on my messages in my app and I want to have a different keystream for each "message group". Therefore, currently I am holding the keystreams in the database ...
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419 views

AES-256 Shift-Rows Offsets

I am currently trying to implement a AES-256 cipher according to this sepcificaciton: http://techheap.packetizer.com/cryptography/encryption/spec.v36.pdf As well as on Wikipedia and in the document ...
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454 views

AES CBC MAC splicing attack

I'm trying to implement AES CBC MAC splicing attack in Python, the idea is: given a message M, its tag Tm (MAC(M) = T), a new message N and its tag Tn we build a message such as: M||N = (M1, ..., Mn, ...
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212 views

simple multiplication in GF(8)

I am trying to do multiplication in the GF($2^3$) defined by the irreducible minimum binary polynomial $X^3+X^2+1$. I want to multiply $A(x) * B(x)$ where $A(x) = x$ and $B(x) = x^2$. The ...
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533 views

Game traffic encryption AES CTR + HMAC

I was asked to implement traffic encryption between the game server and clients. Currently, the traffic is not encrypted in any way, which lets players use cheats to listen to the traffic in order to ...
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Can AES decrypt with a wrong key?

The title is asking the question in layman terms, but what I really mean to ask is this: Let $x \in \lbrace 0,1 \rbrace^{128}$ (an arbitrary input block) and let $K \in \lbrace 0, 1 \rbrace^{128}$ (...
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Diffie-Hellman Secret Exponent Size and Shared Secret Usage [closed]

I'm developing my own protocol and I'll use Diffie-Hellman to achieve PFS. It will work in this way: The symmetric encryption algorithm will be AES_256_CBC. The DH parameters will be: P: a 2048-bit ...
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What does AES256-CTS-HMAC-SHA1-96 mean in relation to Kerberos?

I'm not completely clueless as to what it means, but I'd like to understand it at a higher level. The highest encryption type used by Active Directory domain controllers for Kerberos authentication ...