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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What security risks does exposing the size of the plaintext entail?

For this question my focus is exclusively on symmetric block ciphers (with a particular interest in AES256 in CBC mode). I have read much discussion on various ways to pad the plaintext so that the ...
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How to detect a failed AES256 encryption programmatically?

I have implemented a simple encryption/decryption program based on AES256 in CBC mode1. Actually, it is more precise to describe it as a compression+encryption / decryption+decompression program. If ...
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Any benefit to encrypting IV and MAC in a mode like AES-GCM or ChaChaPoly?

Would there be any benefit to symmetrically encrypting the IV and MAC in an AEAD mode of operation? More specifically would this prevent someone from exploiting the accidental use of a duplicate IV ...
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Generate Private Key with AES 256 CTR [migrated]

How to generate a private key with AES 256-CTR ? I need a private key with CTR as CBC is no longer supported by my client. Please advise Details: We need to connect to an SFTP instance of client ...
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Is this a Matrix for AES, and why?

My task is to check if this S-BOX is an AES S-BOX. My Idear is, that you cant use it because 16 - 10 and 17 - 9 will give you the same output. Given Matrix:
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Decrypt authenticated cipher while still encrypting [duplicate]

Normal AES-GCM generates an authentication tag at the end of encryption. I want to decrypt it while it is still being encrypted. This would be useful to send, encrypt, receive and decrypt a large file ...
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Is the Java function AES/CBC/PKCS5Padding vulnerable to padding oracle?

I have an application that stores data on the devices. Currently AES/CBC/PKCS5Padding from javax.crypto.Cipher(see reference) is ...
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Understanding need for PKI

For simplicity let's say I only have RSA and AES on my hands and I want Alice to talk with Bob over a secure channel. With secure I am implying no MITM and Alice and Bob know they are talking to each ...
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AES-CBC streaming configuration IV usage

I am interested in the implications of using AES-CBC in a streaming configuration. Reading the specifications of a few protocols I notice that when using AES-CBC they include IV + ciphertext + HMAC ...
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Is it possible to truncate AES output and keep uniqueness (no decryption needed)? [duplicate]

I would like to hash numbers less than 1000000000, so generally they could be stored on 30 bits. The aim is to obtain numbers that are not reversible, so my initial plan was to use SHA256 (with some ...
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Is there any asymmetric encryption algorithm for eliptic curve(secp256k1) without AES? [duplicate]

I am looking for asymmetric encryption using SECP256K1. But all over the internet, I see that it also requires AES encryption. Instead of generating an AES secret key, is it possible to encrypt using ...
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Where is the AES-256 key/ IV pair stored in wallet.dat file? [migrated]

I have created an encrypted bitcoin file. I know the password and I see the mkey in the hex dump. I would like to know where the AES key / IV pair are located in the wallet.dat file?
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AES256 key entropy requirements

Is this encryption method sensitive to weak keys? Is there any reference in the NIST on the AES key's entropy? (For example, must it have been generated from a TRNG?) Can I safely use the Microsoft ...
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is it safe to AES encrypt the RSA private key and storing it in the database [migrated]

i'm building an app that really needs encryption of this type , my question is it safe to store the aes encrypted RSA key in the database ? here is how i encrypt the key : i generate a random 256 ...
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Make AES more secure by randomising the blocks in an encrypted file

I am developing a software with hybrid encryption (RSA-4096 and AES-256-CBC). The iv and key of an AES encrypted file will be RSA encrypted end exchanged through a different way than the encrypted ...
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Make AES CBC more secure by destroying each block? [duplicate]

Assume AES in CBC mode is used to encrypt an arbitrary file. The key and the IV are generated out of secure random data and are both different for each file and of proper length and strength. Then the ...
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How secure is a 40 bytes hexadecimal string AES256 encrypted with 50 bytes random password

Problem Assume I have a 40 bytes hexadecimal ASCII string and a 50 bytes random password. ...
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Safe to use 32 bytes of a 64 byte key?

Sorry in advance as I am not very skilled in crypto. I am a software developer trying to create secure applications. I have implemented a diffie-hellman key exchange between client and server. The ...
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Is AES-GCM suitable for per chunk encryption?

I was looking through Google's encryption flow and noticed that they split each file into chunks and then encrypt each chunk individually with AES-GCM with its own key. Since AES-GCM starts to get ...
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AES key schedule. Does it use a KDF to generate the round keys?

So for each round in AES a different key is used, and as I saw the keys are created form a master key. My question is how these round keys are generated. Are they created via a Key Derivation ...
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AES with bigger keys more secure?

Say you were to generate a 512 bit AES key, then encrypted a message by running it through AES CTR 256 twice, with the first and last parts of the key respectively. Would it be as secure as ...
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How does windows 10 v.1803 save the password in the SAM file? [migrated]

I'm doing a search on how windows 10 saves hashed passwords in the SAM file. From this article I suppose that Windows does this: If the password is 123456 and the user has RID 000003E9: CALCULATION ...
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Securely rekey/re-encrypt AES-encrypted file

Suppose I have a big file encrypted using AES (any mode you want) with key kA. I'd like to give an untrusted proxy a kA->kB "conversion key" so that it re-encodes ...
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Generating the Backup Exec AES-256 GCM key used to encrypt/decrypt LTO5 tape drive data

I've got an LTO5 tape that was backed up using Backup Exec (BE), which used hardware compression when writing to the tape. I've been given the passphrase that BE used to create the actual encryption ...
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How many AES 128-bit keys does a MIFARE PLUS tag have?

I know that the question is a bit silly but I dont know how many keys can a MIFARE PLUS tag store in it. Provided that I have a MIFARE PLUS S tag with 4k memory room and the key length is 128 bit, ...
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Secure Communication

Focus: I have to design a secure keep alive communication protocol and was wondering if it was necessary to sign the ciphertext after the session key has been generated as an attacker will not know ...
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Alter CBC plaintext by altering IV [duplicate]

I am building on this answer. Essentially I have an initialisation vector $iv$, a ciphetext $c$ and a plaintext $p$. The plaintext was encrypted using AES CBC. The aim is to modify the first 4 ...
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I need to send 16 bytes using ECC keys on a resource-constrained device

I have a system where a resource-constrained device has to send 16 bytes. It has its ECC key pair, and a peer's Public ECC Key. We're using the p256 curve. The device also has an AES-128 hardware ...
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What are the length of ciphertexts when 16 bytes and 18 bytes of plaintext using ECB?

What are the length of ciphertexts when 16 bytes and 18 bytes of plaintext are encrypted with AES using ECB mode?
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Can you derive a 128 bit AES encryption key using PBKDF2 with SHA-256

I got confused about key derivation functions. For my project, I need to derive a 128 bits AES encryption key in CTR mode. To do so, I'm using a PBKDF2 to derive this encryption key using an initial ...
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In AES-256-CFB, does using a pseudo-unique key circumvent the weakenesses of reusing keys?

Disclaimer: I'm not very familiar with the subject. Apologies for how that reflects in the question. Goal: Encrypt multiple messages using the same key Hypothesis: If we use, as the actual ...
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Do I still need SHA256 if I already had a AES 256 key that is 44 characters long?

Several months ago, I was required to research on AES and SHA-256 to make a secured license system for my app. However, I was dumb enough that couldn't distinguish between the 256 bits from AES and ...
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AES - CCM, why not use CMAC inside instead of CBC-MAC?

I was reading up on AES-CMAC when I learned that this basically is an improved and more robust version of CBC-MAC, with the ability to safely have variable-length messages. Difference between CBC-...
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Bluetooth Low Energy: Key generation

I'm studying the BT core spec v5.1 to understand the security features and how everything fits together. I am looking at Secure Connections for now. In the field "Key generation" it says it uses P-...
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how can I test quality of sbox?

I have 11 sboxes, I want to test them and find the best one. How can I do that, I found several criterions for that but I could not understand.
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Any white-box cryptography for asymmetric-key? What is the latest status of white-box cryptography?

I am learning white-box cryptography. So far, I find the following historical research or implementations, for examples: Published white-box AES algorithms E.g., Chow's WB AES and WB DES (2002), WB ...
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Determine Encryption Used by Examining File Headers?

I have an encryption problem that I hope you might be able to help me with. I have a bunch of encrypted files. Some of them were encrypted with ...
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how to compute Bit Independence criterion of SBOX?

I want to compute BIC's of my Sboxes, I found out some theses for that but I could not understand how to do it. Can someone help me?
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Can you defeat AES-CTR's birthday boundary with a 2nd AES?

This follows on from How do I produce a stream of secure random numbers from AES-Counter mode? Consider then the generator:- $$ \operatorname{AES_{k1}}(n) \oplus \operatorname{AES_{k2}}(n) $$ ...
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Retreive secret key and IV knowing the plaintext and ciphertext?

If I use AES-128 in CBC mode, and I know the plaintext, ciphertext, and length of the plaintext padding, which is 15, can I retrieve the key and IV, using brute force or some special techniques?
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Explain mixing bijection with an example

I am reading whitebox AES. "Mixing Bijection" is one of the important definition. For example, I copy one paragraph here: The look-up tables that incorporate bytes of round keys can be considered ...
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How to generate whitebox AES decryption algorithm and code, with existing WB-AES encryption code?

I can find several whitebox AES 128 implementations on Github, such as wbaes-1, wbaes-2, wbaes-3, etc. All of them are developed based on WB AES encryption. Ideally, most implementations include two ...
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What encryption shoud I use for single char encryption?

I'm very new to encryption and I wanted to know if it is secure or just possible to use encryption on single chars. I did some research, but nothing to clear and i'm a bit confused. The modes I think ...
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how are variable key sizes produced?

I am current learning the internal working of several Symmetric key Cryptographic algorithms, and came across DES and AES. DES takes in input a 64 bit key and AES-128 takes in input a 128 bit key ...
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Collision Security

Question concerning collision issue in CBC-mode: If we are using CBC mode with AES for 1 message, the birthday paradox indicates that we risk a collision after 2^(n/2) so 2^64 plaintext of 128 bits of ...
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Encrypt UDP packet with time-generated encryption key

I'd like you to help me solve a dilemma of mine. I am currently building a home automation from scratch for my next house. The basic gist of it is that I will send UDP packets over a local network. ...
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AES-GCM cipher - Nonce vs IV

I am using a Python library called PyCryptodome, which offers the following API for AES-GCM ciphers: https://pycryptodome.readthedocs.io/en/latest/src/cipher/aes.html As you see, IV is not ...
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AES encryption question

If we consider the generation of keys as $$\begin{aligned} K_0 &= E_K(IV); \\ K_{i+1} &= E_{K_i}(A) \end{aligned}$$ Where A is a block of zeroes, and the ciphertext blocks are computed as ...
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How are these AES MixColumn multiplication tables calculated?

I'm using the mul2, mul3, mul9, mul11, mul13 and mul14 tables for the MixColumn and InvMixColumn steps in AES-128. However, I got these off some Github repository, and now I'm looking for an actual ...
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aes invmixcolumns process? [duplicate]

I want to know how to obtain mixcolum -> invmixcolumns mixcolumn = [2 3 1 1 1 2 3 1 1 1 2 3 3 1 1 2 ] -> -1/35 [4 3 11 17 17 4 3 11 11 17 4 3 ...