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

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How does AES-CCM work in BitLocker?

I'm studying this white-paper: http://jessekornblum.com/publications/di09.pdf The author says that using AES-CCM with the external key (highlighted in green at page 9, figure 4) and with the nonce at ...
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52 views

Modes of Operations Exercise

I am currently stuck at an exercise for my Cryptography Class in University which is: Alice wants to send a message $M = (M_1,M_2) =$ "Pay Bob \$100 from bank accout $12345$" to her bank (encrypted). ...
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36 views

For enciphering messages with AES in CTR mode, do I need a different key for each message?

I have written a program to run AES in CTR mode with keys of 128,192 or 256 bits and checked it gives correct results with the data given in section F.5 at ...
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104 views

Simple way to extend AES to 256-bit block size

What is the best way to use standard AES with a 128-bit block size to act as a 256-bit block cipher? I am aware of CMC and EME which seem to serve this purpose, but they seem to be more complicated ...
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18 views

Cryptography — with a semi-priveleged user in the middle — to prevent request-tampering with another server

I'm working on a chat server for a mobile app I am writing. I would like to use a different application server for non-chat related operations and another application for chat operations. I would ...
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63 views

What is a 'secret key factory'? What precisely is it doing? [closed]

I have found a Java implementation of AES CBC mode that runs in Netbeans. The lines below appear to create the key from password and salt: ...
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74 views

How we transfer 128bits cipher to a 4x4 matrix for AES input?

Why the input cipher for AES encryption, can write in 4x4 matrix with 8 bits entires, and can said is 128bits? if each cell is 8bits in binary, how we said this matrix is represent 128bits?
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36 views

Separate TLS Client Write and Server Write Keys in AES-CCM Mode

I am designing a system that uses TLS-like handshaking on a resource-constrained embedded system. I have settled on AES-CCM mode for symmetric session encryption and authentication, allowing ...
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113 views

Is this a secure (and correct) sign-then-encrypt technique for transferring messages?

After reading some information on the way iMessage works I have been working on writing some code to try my hand at securely transferring messages in a similar manner and I wanted to confirm that the ...
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111 views

AES encryption takes more time to decrypt than encrypt

Please let me know if this is not the right place to ask this question. I will remove it. I am trying to find how much time an AES encryption and decryption takes for a given amount of data and key. ...
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25 views

Is there a flaw in whole disk encryption vs volume or folder encryption? [duplicate]

My company just implemented whole disk encryption on all laptops (Symantec) and the concept seems flawed. Please correct me if I'm wrong, but if I have known file in plain text and that same file in ...
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70 views

What is the forward cipher function of AES-XTS?

We're using OpenSSLs EVP_aes_265_xts encryption on data (with unique, random, IVs for every new message encrypted) - which is working well. But, I've been asked; what is the forward cipher function ...
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135 views

Is there any analysis of freebsd's “geli” encrypted geometry provider?

I've done a few obvious searches on google and google scholar and not turned up any security analysis of FreeBSD's geli. Is there some out there, or has it gone unanalyzed since its introduction ...
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45 views

AES and Known-plaintext attack [duplicate]

Can you help me to finding some papers that shows AES is secure against known-plaintext attack?
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40 views

one-time key, zero IV in stream cipher (e.g. AES-CTR) [duplicate]

Say I am using a random key to construct a stream cipher with, say, AES in CTR mode, which will never be used to encrypt more than one data stream. Is there any advantage, no matter how small, to ...
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93 views

openssl logs showing keyblock length of only 88 bytes instead of 136 bytes

I was decrypting TLS encrypted data from wireshark using the openssl(TLS1.0 version) TLS logs which provides the complete key block which of size 136 bytes.Now i moved to TLS(1.2 version) in that Key ...
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243 views

Non-malleable file encryption using AES XTS 256?

I'm looking to do file encryption of a bunch of individual files, some small, some quite large. The files will be write-once/read-many, so I could use CBC, however, since the read-access needs to ...
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1answer
180 views

Using AES-CBC and providing the IV in file header -> security hole? [duplicate]

currently I audit some code I've written in the past to use KeePass 1.x databases. I stumbled over the following question: The database itself is decrypted with AES-CBC and inside the file header the ...
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120 views

Security of .net AES implementation and security of a hash MAC

My question rather splits into two sections: Is AES correctly and security implemented in the .net Framework? Are there any reviews of implementation mistakes that would weaken the security of AES ...
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1answer
247 views

Random Number Generator based on AES CTR

I've just about done tinkering with an open source DRBG, and I sure would appreciate a bit of advice from this community. Here's the link to the project, hosted at codeproject.com. It is written in ...
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2answers
176 views

Should an AES byte key generated with OpenSSL be converted to hex?

I am generating a key & iv with Ruby's OpenSSL wrapper for an AES CBC 256 setup: ...
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2answers
558 views

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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2answers
160 views

Is this how padding can work?

So for block ciphers you need a fixed size block. If the plaintext length is not a multiple of the block length then you need to pad it. One way you could do this is that for the last block you just ...
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1answer
98 views

AES 128bit round level recommendation

we don't want change standard just after every attack, now for AES 128bit blocks i think 16 round is secure, but what is best round amount ? we had attack for 7 round then 10 round and it going so on ...
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354 views

Is the AES encryption scheme CPA secure?

Give a 256 bit key space and 128 message space would AES block cipher as the encryption scheme be CPA secure?
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202 views

Decrypt AES-128 with key file but missing IV? [duplicate]

I want to decrypt a file that has been encrypted using AES-128 in CBC mode using OpenSSL. I got the “.key” file – which is 32 digits – but when I try to decrypt with OpenSSL, the program asks me for ...
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98 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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1k views

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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1answer
290 views

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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132 views

The security of the AES secret itself

I am writing an application, running on a server, where multiple users access data from a database which is AES encrypted with a master secret. The master secret itself is initially randomly ...
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1answer
192 views

brute force attack on KDF vs KEY

if we believe 256bit keys are secure in AES against any brute force attack, is that possible we use a KDF (convert user's weak entered password in truecrypt into a fixed AES key) with too much round ...
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2answers
61 views

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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1answer
147 views

Encryption and HMAC key derivation

I'm deriving keys from a user-supplied passphrase for symmetric encryption using AES-256 in CBC mode with a HMAC for authenticity/integrity. My key derivation function currently looks like this: ...
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1answer
77 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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1answer
378 views

Is AES reducible to an NP-complete problem?

Is breaking AES NP-hard? Can the security of AES be reduced to a NP-complete problem? If it is reducible, what does the reduction look like? If it is not reducible, why do we assume it is secure?
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198 views

What is the complexity of the Square attack against the reduced 4-rounds 128-bit Rijndael variant?

I'm looking at a square attack against a reduced version of AES-128 with only 4 rounds (with block and key size of each 128 bit). I have a set of 256 plaintext-ciphertext block pairs. What is the ...
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1answer
168 views

Design criteria for AES

I hope somebody can help me understand the design criterias for AES. Therefore, I would be really thankful if somebody could explain "non-linearity" in this context. A criteria for the s-box in AES ...
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1answer
68 views

AES CBC encoding of decomposable OAuth2 tokens

We're building a stateless RESTful API that relies on the content of OAuth2 tokens to identify users and what they have access to. Users authenticate with other means and are given a token, which they ...
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1answer
262 views

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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1answer
218 views

Appropriate AES key length for short term protection

Currently I'm doing some initial research for a fully connected distributed network communication model. The context here is a peer-to-peer multiplayer protocol, using a majority-voting system. More ...
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1answer
125 views

Is AES a linear hash?

So, having read a variety of documentations on AES encryption, I came to the unknowledgeable conclusion that the key schedule applied to the array of chunks, and not just the 14 cycles on a single ...
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2answers
558 views

Deriving HMAC key and cipher key from passphrase? [duplicate]

I'm encrypting a file with AES-256 in CBC mode. I needed to add an HMAC for authentication and validation of the file contents and passphrase, so I used a SHA-256 HMAC over chunks of my file ...
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32 views

Different Diversify key, every time with AES-CMAC [on hold]

I am using the following code and class to generate a diversify key from AES_CMAC. The doFinal method returns different key every time given the input and masterKey are constants. Any suggestion would ...
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37 views

OpenSSL: do I need multiple EVP_CIPHER_CTX structures? [migrated]

This may need to be on StackOverflow instead. I have a single-threaded client/server application that needs to do both encryption and decryption of their network communication. I plan on using ...
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61 views

AES/CBC fixed Initial vector use-case [duplicate]

I am using AES/CBC to encrypt my http cookie. I never encrypt the same cookie value twice so my understanding is I don't need to use a random initial vector - using a fixed initial vector is fine for ...
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1answer
233 views

AES CBC Security

I am building an Apache webserver with TLS 1.2 and OpenSSL 1.0.1. So far, I have enabled 2 encryption algorithms - ECDHE AES256 GCM and ECHDE AES128 GCM. Firefox and Chrome(ium) use NSS which ...
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102 views

How many messages needs to be send to server to get AES key in Cache-timing Attack

I'm trying to evaluate the correlation between key length and the number of messages that needs to be send to server during Cache timing Attack. I read both D. Bernstein, “Cache-timing attacks on ...
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42 views

NIST Standard for Advanced Encryption Standard Algorithm [duplicate]

Possible Duplicate: Advantage of AES(Rijndael) over Twofish and Serpent What is the reason of NIST why Rijndael choose as the Advanced Encryption Standard
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328 views

how much is secure to encrypt a password using itself (as encryption key) for storing it on a unsecure media?

I want to store a password securely on a storage (suppose in a usual unencrypted file). I use this password as AES key to encrypt itself (using AES-ECB) & then store it on the media (the password ...
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1answer
126 views

Understanding multiplication in the AES specification

I am reading through the AES specification and am not able to wrap my head around the multiplication definition (section 4.2). Sorry to refer to a spec but AES is the holy grail in crypto so I hope ...