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Questions tagged [initialization-vector]

Unique data used by block cipher modes of operation to randomize the output in order to achieve semantic security. Also for other similar constructs in other iterative algorithms.

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Tools for key & IV generation [closed]

Any well known tools you know to generate (better CSRNG based) keys and IVs ? for windows , preferable from know verified sources.
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Does the Initialization Vector in DES have to be 8 bytes long?

I was experimenting around with DES and decided to implement an IV (Initialization Vector) for it. I noticed that in DES, which is 56 bits and 8 parity bits, the IV would be 8 bytes in length. Does ...
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Given the key, the plain text and the cipher text can I calculate the IV used in CBC mode?

If I have the plain text, the ciphertext and the key for an AES-128 CBC operation, can I determine the IV, even if I don't know the padding (assuming the padding follows one of the more common formats)...
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Security implications of not concatenating a 1 to the IV when using GCM

When using GCM, The padding string $0^{31}||1$ is appended to the IV. I know that this is done to avoid the repetition of $E_K(0^n)$ which is used as key for the GHash. But what would be the security ...
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How to generate a 128 bit IV from a 32 bit value for AES-128 OFB

I have no clue how to determine suitable 128 bit IV (initialization vector) from a 32 bit IV. Encryption AES-128 OFB. The 32 bit IV has value 0x9a23773c (...
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How does reusing IV for OFB mode breaks the scheme

Consider a Plaintext P1 and Ciphertext P2, which is known to the attacker. If the attacker knows that the IV used in encrypting P1 in OFB mode is the same used to encrypt another plaintext P2, how can ...
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2answers
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using different IV and SALT with AES-CBC but same KEY

I'm working on this project where a client can send a message, now obviously sending it in plainText is not very smart. So I decided to Encrypt it with AES-CBC. Now, each time I encrypt something, ...
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Is it safe to compute HMAC(Base64(IV) || “,” || Base64(CipherText)) instead of HMAC(IV || CipherText)?

Let || be the concatenation operator. Let CipherText = AES(Key1, IV, Message). Let us assume AES is used in CBC mode. I want ...
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AES Cipher Block Chaining 128 bit message

I understand that for AES CBC you need to split the plaintext up into blocks and perform XOR'ing using the previous blocks calculations etc. However, if your message is exactly 128 bits long, do you ...
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1answer
96 views

Best practices for IV generation

What are the best practices for IV generation for AES and other algorithms? Is RNG enough? What if I cannot use RNG and need to use a variable that is related to some characteristic of the ...
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Is it possible to encrypt a message stream with the same IV each time and for it to be secure?

I know we should ideally never reuse the IV (Depending upon the mode of encryption used), but is it possible to have a protocol which uses the same IV for the message stream and is as safe as one ...
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1answer
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Attacking Double DES (OFB Mode) given the initialization vector and not much else? [closed]

I'm given a Plaintext/Ciphertext pair, a Ciphertext to break, and the IV. One thing of note is that the same IV is used for both DES Encryptions, so $$C = E_{K_2}(E_{K_1}(P, IV), IV)$$ I have limited ...
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Can I use a fixed IV with AES-GCM if I only encrypt unique plaintext values? [duplicate]

My use case guarantees that all plaintext values are unique. In this case, is it safe to use a fixed IV with AES-GCM to carry our encryption/decryption?
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Is the AES-GCM encryption using the SHA256 hash of the plaintext as IV secure?

I want to encrypt a list of unique values and I want the property of when I encrypt the same value I get the same ciphertext (determinism). The adversary only observes the ciphertexts of a unique set ...
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1answer
325 views

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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It is the IV shared in CBC mode?

I don't know if the IV in CBC mode is equal in both sides of the encryption and decryption operations. I know that the IV must be unpredictable, but has it to be MACed in the encryption side to be ...
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1answer
635 views

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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What happens if you increment MAX counter in AES-CTR?

Suppose you use a IV/counter = ffffffffffffffffffffffffffffffffin AES-CTR. What will happen if you encrypt the next block, and thereby increment the counter by one? ...
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Signal Protocol Header key encryption initialization vector

In Signal Protocol when you use a Double Ratchet you have 2 options: Normal encryption = header + ciphertext Encrypted header encryption = ...
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Why BouncyCastleAesCbcBytesEncryptor is using a salt and an initialization vector?

I'm using the class BouncyCastleAesCbcBytesEncryptor from Spring Security. One of the constructor has the following signature: ...
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IVs in WEP encryption

First, I'm pretty new to the world of encryption. As I understand it, in WEP, the plaintext and CRC are XOR'd with the IV and the key (or more accurately, the key/stream, which is produced by a pseudo-...
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Is it possible to recover the key to a decrypted file? [duplicate]

Is it possible to recover the key to a decrypted file if you have the initialization vector and it uses RijndaelManaged in CBC mode? If so how? The file I want to recover the key from is a xml that ...
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Can a zero nonce be safely used with AES-GCM if the key is random and never used again?

I could generate a random nonce and prepend it to the ciphertext, but storage space is at a premium and the only constraint AES-GCM has on the nonce (if I'm reading correctly) is that the same nonce ...
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What is the most secure way to encrypt certain properties in logs

I would like to encrypt certain data before logging it. Currently, I use a private key and a static IV. Looking at generating a suitable IV I am concerned about the overhead in generating CSPRNG ...
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Randomly initialised global counter used to encrypt the kth message with IV = IV + k mod 2^n

The use of an increasing IV is not secure for a block cipher. That is, using a random IV for the first message then IV + 1 for the second , IV + 2 for the 3rd etc. How can I construct an attack to ...
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1answer
374 views

IPsec : transmission of Initialization Vector

I am currently carrying scholar research about IPsec protocol, and I have a question regarding the IP Encapsulating Security Payload (ESP). Is the initialization vector of operation mode transmitted ...
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IV Re-use and Chosen Plaintext against 56bit Blowfish (CBC)

I am looking at a very old protocol which uses Blowfish to encrypt packets with a constant 8-byte IV in CBC mode. Assuming I have: The ability to arbitrary encrypt known plaintexts The IV I know ...
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Maximum key stream sequence per key/IV pair in communication protocols

In the paper "LIZARD – A Lightweight Stream Cipher for Power-constrained Devices", one of the design rational of Lizard cipher is key stream size per key/iv pair. A5/1 produces only 228 keystream ...
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AES-GCM cipher tag and IV size, while attempting to render encrypted ciphertext useless by removing them

I'm using AES in GCM mode of operation for encryption/decryption & authentication of segments of data in a file. The layout of each segment can be summerized by this diagram. Each segment is ...
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how to compute IV with AES CTR if key, plaintext and ciphertext are known?

Given $E_k$, which a block-cipher using the (known) key $k$, and a plaintext-ciphertext pair $(p,c)$ where $c$ is the encryption of $p$ using CTR mode, can the initialization vector be recovered using ...
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Is it required to use a random IV for AES-CBC with random key per message? [duplicate]

I'm developing a program to encrypt and decrypt a file with AES-256/CBC in Java. And I want it to be safe enough. In my case, I generated random AES key for each file to encrypt and decrypt them. My ...
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1answer
230 views

Alter plaintext through IV in block cipher AES in CBC mode

IV: 69bb375aa919c72aa561dd7b7ffacf66 Ciphertext: "c28ea025d10186510855d083747d6435c808d9857075abd9bfc54b094e60eaf3" Plaintext: "SEND ENCRYPTED DATA" I want to be able to change the resulting ...
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AES-256 GCM IV guidelines

If I use for example AES-256 (GCM), and my message is bigger than 256 bit (broken into smaller 256 bit blocks for encryption), should the IV change for every 256 bits of the message?
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1answer
178 views

AES-256-CBC with random IV - storing same plaintext as same ciphertext

I am encrypting some information stored in a column of a MySQL database. The column can contain repeated values, let's say the table has 7 rows and the column to be encrypted has the following values:...
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1answer
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Why can´t an attacker find the key if he has the plain text, the IV and the ciphertext? [duplicate]

I am reading a book about web security and they are now talking about AES CBC. After reading the chapter I was wondering, can an attacker compute my secret key if he has access to the IV, the plain ...
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1answer
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With AES-GCM, may I use multiple tags per key?

In my implementation of AES-GCM, the key might change only once per minute. However, I wish to calculate a new tag every 6us, to reduce latency (since you have to buffer up a GCM "packet" before ...
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2answers
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Safely erasing encrypted data

My secret message is encrypted in a byte buffer with AES-128 in CBC mode. The first 16 bytes are the IV and the message follows contiguously. If I want to securely delete this message is it enough ...
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1answer
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Is an IV useless for encrypting database IDs?

In my scenario I need to build a pseudo-anonimization service: a machine that given a plainID return a chiperID and vice-versa. <...
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1answer
199 views

Crypto-shredding a file by erasing the IV instead of erasing the Key

Imagine an authenticated, encrypted file system, which uses AES-256-CTR to encrypt a 64 KB file sector, then uses HMAC-SHA256 to authenticate the 64 KB file sector (including the IV). IVs are 128-bit, ...
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433 views

Simulation of Chosen Plaintext Attack on CBC, Predictable IV with OpenSSL

I would like to simulate the CBC IV attack where the IV is predictable. It's described in the answer to this question: chosen plaintext attack on CBC, predictable iv (Only "Yes" and "No" are valid ...
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1answer
182 views

Recovery of private key in AES-CBC from two ciphertexts with different IV, but identical plantext

I have a system that encrypts messages for a given user using key K using AES-CBC in response in an external stimulus. Each message has a randomly generated IV. The user never decodes these messages,...
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Encryption using deterministic CSPRNG as secure as CSPRNG

As a beginner it seems that a scheme derived from a CSPRNG should be as secure as that CSPRNG. Is this a correct assumption? Are there restrictions or known special cases? A rough outline would be: ...
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1answer
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Does it matter how the IV and XOR are applied for a single AES-128 block?

I want to encrypt 128 bits of data. I understand the problem with ECB, so I generate a 128-bit Initialization Vector to use for encryption and send with the encrypted data. Is there a "best" way to ...
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2answers
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Can I find the IV of a single block of SHA256, given the plaintext and digest?

Each 512-bit block of SHA256 takes an initialization vector (IV) and message schedule and returns a digest. Knowing the message schedule and resulting digest, is it feasible to reverse the algorithm ...
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1answer
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Decrypting an encrypted aes 256 cbc text with random IV, decrypts the string [duplicate]

This may be a basic question but bear with me. I started encrypting a text with aes 256 cbc mode generating a random iv of 16 bytes and a key. ...
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Encrypting current time using 3DES as a signature

I came across a peculiar system for generating "signatures" ("signatures" is within quotes because this is a bad use of 3DES) in the wild. It works as follows: a symmetric key is generated and used ...
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Does an IV need to be used in AES CTR mode?

If I encrypt a message once using AES CTR, will I need an IV? Additionally, if I do use an IV, will I need to send it with the cipher text?
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265 views

Is it ok to transmit an IV as a custom HTTP header?

Considering an AES OFB encryption algorithm, suppose that I'm sending a message over HTTP (not HTTPS) and my message body contains the cyphertext. I'd like to know if transmitting a random ...
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1answer
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Doubts regarding implementing AES-128 bit algorithm in my IOT system

I want to implement AES-128 in my IoT network which consists of a Master device which runs Linux on it and slave devices which are 8-bit micro-controllers that periodically transmit data packets to ...