Questions tagged [aes]

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 any part of AES encrypted blocks be used as PRFed value?

Suppose we need a PRF whose output space is 255bit. Then, what I can do with AES with 128-bit security is producing 2 AES blocks that are of 256-bit. Then, I will remove the most significant bit of ...
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Behavior of AES-CTR with 128-bit nonce and possible overflow

If I feed 128 bits of randomness into AES-CTR as its IV / nonce / initial counter, what will happen if I feed in a random 128-bit integer that overflows and wraps around? I've written a test for this ...
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How to use Whitebox aes

There are server programs and client programs. ・Prepare two keys (A, B) for AES. ・The A key creates an encryption table in advance with WhiteboxAes. ・The B key creates a decryption table in advance ...
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Prime fields vs non-prime fields

I was watching this class about AES in this LINK and I was trying to grasp the concept of prime fields, which is a finite field with prime order $p$. The non-prime field part (order is $p^n$) is ...
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AES S_BOX Generator additive constants

I try to generate other S_BOX for AES but I don't realize how to choose additive constants for S_BOX from decryption if for encryption it is 0x63 why is ...
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A possible error in the book

So I have been reading this book called "Implementing SSL/TLS using Cryptography and PKI" While going through it, this snippet of code got me baffled ...
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Can you derive the AES key if both cleartext and ciphertext are known? [duplicate]

If you have a single 128-bit block data in cleartext and the exact same data encrypted with an unknown AES key (the key length is known, though), is there any possibility of determining that key other ...
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Line by line encrypted logging stored with iv/salt/iterations. How safe is it?

I'm building an encrypted logging application. Log entries are encrypted with AES-256-GCM, using password-derived keys with PBKDF2. The application must support log rotation, and I would like to make ...
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modified AES-CMAC algorithm

I want to use AES-CBC for secure firmware upgrades on a microcontroller, with AES-CMAC for checking the integrity of the firmware image. The AES-CMAC algorithm needs a AES-128 encryption funtion. For ...
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How to calculate new AES keys for NFC application?

I want to program a couple of AES-enabled NFC tags (for example these) with some custom data, and secure these tags by using the AES features of said tags . In order to increase security, i want to ...
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How to implement a Bit-Flipping attack on AES-CBC? [migrated]

Performing a task with root-me.org, as I understand from the attack statement, it is necessary to perform a byte shift to receive is_member = true After reading some instructions, I supplement the ...
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Can I use aes-gcm to authenticate a user based on his ability to decrypt a payload?

I'd like to authenticate my users without storing their password, even in a derived form with scrypt/pbkdf or other derivation methods. I'm exploring the idea of encrypting a random payload with AES ...
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data privacy, integrity and authenticity of distributed firmware images for an embedded device [closed]

Please assess the following suggested decryption and signature verification scheme. This is somewhat related to Types of Cryptography for a 4-8 bit microcontroller and similar to How to enforce data ...
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NTAG 424 - how to diversify the key?

I am currently working with the NXP NTAG 424 chips, which feature AES-128 encryption. In the end, one will be able to read an NDEF message; for example, with a smartphone, the backend server will ...
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Size of IV in AES-GCM according to RFC 4106

RFC 4106 specifies about nonce. It contains a salt of size 4 octets and an iv of size 8 octets. Further, RFC specifies that salt is assigned at the beginning of the security associations which is ...
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Cryptography question(s) about RSA [duplicate]

In the real world, it's best to use at least two or more algorithms to encrypt data. From what I know, RSA acts as a wrapper to transfer data safely across web systems or API(s), or acts as a wrapper ...
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Scheme to verify AES key was correctly encrypted for public key recipient

In our file sharing scenario there are three participants: $A$, $B$ and $C$. Each participant has a public-private key pair (let's assume RSA for now). $A$ wants to share a symmetric AES key $k$ with ...
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Encrypting text with AES and MPC

I'm thinking of implementing text encryption and decryption in my program using AES using key sharing thanks to MPC (the point is that the key should never be provided in full), however, all public ...
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Is it safe to distribute different portions of the same data encrypted with different AES keys?

Assume I have a block of data consisting of three segments A, B and C. With "segments" I mean a particular section of a bit stream, so if the whole binary data was simply ...
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IV generation best practice for AES-256 CBC

I saw some SWIFT code that generates IV for AES 256 from selecting 16 characters from a-zA-Z0-9 space. Is this secure? Sufficiently secure? What is the best practice to generate IV for AES 256? Will ...
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Can I make fixed-length ciphertext with AES-256-GCM?

I have a question about AES-256-GCM encryption. Can I make a fixed-length encryption output? In my understanding, I cannot make a fixed-length ciphertext. To me, the fixed-length output is much more ...
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Using AES-GCM (or AEAD ciphers in general) as a pure MAC without encryption

What's the opinion on using an AEAD cipher such as AES-GCM for example as a pure message authentication code (MAC) when only message authentication but not encryption is required. does it bring any ...
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Prove that the $x^8+x^4+x^3+x+1$ is irreducible over $\mathbb{Z}_2[x]$

I am new to this field. I am doing some cryptography course and have encountered $\text{GF}(2^8)$ in the famous AES algorithm. Although I do not have a strong relevant math background with this stuff(...
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What algorithm for AES key wrapping to choose in an embedded environment

In an embedded environment, what AES key wrap algorithm is best, in terms of performance and security coverage? We are using RSA PKI asymmetric encryption.
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How to design a secure challange-response authentication protocol?

I am implementing a custom challenge-response protocol to authenticate a client to a server. Mutual authentication is not required, i.e. the server doesn't need to be authenticated to the client. The ...
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How do byte-sliced AES implementations work?

While I understand the principle of bit-slicing, several papers mention byte-sliced AES implementations (see e.g. Homomorphic Evaluation of the AES Circuit and Fast Implementations of AES on Various ...
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Using 0 nonce for AES-256 in CTR mode

My question is: I'm using AES with 256 bits key in CTR mode. Will it be less secure if I use a random key and static zero nonce? key = random; nonce = 0;
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Why GCM operation mode with AES-128 is recomended and can we use AES-192 and AES-256 with GCM?

It happens that on the internet I often find that AES encryption should use a 128-bit key only if it is used in conjunction with the GCM mode of operation. Why only with 128-bit keys? What happens ...
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multiplicative inverse [duplicate]

I actually do want to know how to generate the multiplication inverse (M.I) table, I mean the calculation how the M.I been generated.. such as the M.I of 22 is 5A regarding to the table.. Do you know ...
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Binary verification of application image before loading it into DRAM

Working on a boot process where the application image has to be verified before loading it into DRAM. We found 2 strategies; RSA-1024, where the private key is secure in premises and the only public ...
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Is there any practical use of reduced rounds of AES

There are lots of attacks which are on reduced block ciphers. There are practical attack on five rounds of AES-128five rounds aes broken in six minutes. I was just wondering if there is any practical ...
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Why can't ransomware practically use RSA to encrypt all files?

I understand that a few ransomware have used an RSA public key to encrypt all files belonging to the victim. This is a bullet-proof system in terms of its security because the private key is always ...
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OpenSSL not producing messages of expected size

I have a 16 byte file, and after encrypting it, its size weirdly changes. ...
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7zip : Why does encrypting the same file with AES-256 not give the same output?

Using 7-zip 19.00, on Windows 10 1909, build 18363.592, I encrypted a text file with the contents "hello there" using AES-256 and the password "123". I did this two times, the exact same procedure, ...
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How to encrypt huge amount of data using AES-CTR

As far as I know, AES-CTR depends on nonce. If I will use same key and nonce for encrypting 1 block of data and another - it will be unsecure. So, how can I encrypt a huge block of data (about 1GB) ...
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Why is it difficult to encrypt large amounts of information using quantum key distribution?

An article last month claimed that Toshiba Corp. and Tohoku University recently broke the record for the amount of data encrypted using quantum key distribution by transmitting "a few hundred ...
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AES-128-CBC padding size [closed]

I'm trying to figure out how padding works by seeing what happens when I try to encrypt a 16 byte file with AES-128-CBC. My understanding was if I encrypt a file of size, say, 28, then there would ...
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How to crack rar file with protected pass with only the AES-256 key [closed]

I have rar with protected pass.But I have the AES-256 key can I crack it and if I can. how?
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AES PKCS5 Padding when it's not needed

I'm using AES/ECB with PKCS5 Padding (From what I've read, PKCS7 Padding is actually used internally) and PBKDF2(HMAC-SHA256) to encrypt some passwords in Java. I enter a password, that goes through ...
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IND-CPA security of mode of operation using triple AES with plaintext || IV+counter

I have found this figure of a mode of operation using a triple AES with m||IV+ctr input: I suppose it's a custom mode of operation since I haven't seen it anywhere else. My question is if it is IND-...
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Key length and message length in AES and perfect secrecy if plaintext length <= key length

As I understand it, a plaintext encrypted using a One Time Pad is uncrackable because all possible plaintexts of the same length are possible. As a concrete example, if you decrypt the first 3 bytes ...
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What is DLf3072s256mRijndael cipher suite?

We have a Thales HSMS and upon going into the Cipher Suite, we have the DLf3072s256mRijndael cipher. What is this cipher and how does it work? Is this an AES encryption? What does DLf mean? what ...
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is it true that AES initialization constants which are supposed to be random numbers are in fact chosen by NSA?

is it true that AES initialization constants which are supposed to be random numbers are in fact chosen by NSA? i mean its said it was done before algorithm standartization back when it was still ...
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The security effect caused by an MDS matrix in word-oriented designs

Considering a design where the MixColumns operation of AES is replaced by a lighter MDS matrix where by the term lighter we mean the number of required XOR to implement an MDS matrix. As you know ...
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AES S-box and Nothing Up My Sleeve

Cryptographic primitives should have nothing-up-my-sleeve property to prove their designers don't have an advantage in using them versus the general public. For example, Blowfish is using binary ...
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On AES at the MixColumns why may the algorithm use several Galois Fields depending on the Key size?

On AES at the MixColumns why may the algorithm use several Galois Fields depending on the Key size? Also, why must the polynomial P(x), from the galois field matrix multiplication mod P(x), be ...
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Is this correct/incorrect password for file encryption scheme secure?

I'm writing an AES file encryption program, and I'd like to put in a way to tell whether or not the user has entered the correct password without decrypting the entire file and GCM telling me the tag ...
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what if key of aes will be more than 32 bytes? [duplicate]

For example, if I use AES-CTR and use key of 44 bytes. Will it be breakable or not and why? How to use AES-CTR correctly?
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Why are AES keys increments of 64-bits?

Why are AES keys increments of 64-bits? Rijndael, which subsequently became AES, allowed key increments in 32-bits (128, 160, 192, 224, and 256 bits). However, AES made it 128, 192, or 256. My guess ...
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Do I need to encrypt the IV?

For example, I'm using AES-CTR. I use fixed (random generated) key and random IV. I know that I have to encrypt key but I don't know about IV. If I will encrypt 1 block of data with fixed key and ...

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