Questions tagged [ofb]
Output Feedback Mode (OFB) is an encryption mode, that builds a synchronous stream-cipher from a block-cipher.
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How is the IV/Nonce determined in OFB mode? - SQLite Encryption Extension (SEE)
I am doing some research in different methods of encryption for SQLite databases. One of the databases I have is AES-256 OFB encrypted with SEE (https://sqlite.org/see/doc/release/www/readme.wiki). ...
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Vulnerability due to same IV, same key, same plaintext at same position in OFB
I am currently studying OFB mode, and one of the vulnerability mentioned for it is that if two different messages have a block at the same position in the ciphertext, and have same plaintext, the ...
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Would an encryption-only block cipher be useful at all?
I recently implemented AES block cipher, encryption side only, to be used in QUIC parsing (QUIC uses GCM mode). There are other modes than GCM that use only encryption: for example CTR, OFB, and CFB.
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Can you use Output Feedback Mode (OFB) to construct a Message Authentication Code (MAC)
Suppose $f_k$ is an arbitrary block cipher. Can OFB via $f_k$ be used to make a MAC. I argue that you can't even with fixed l, $m = l \times k$ because in OFB, $\mu = f_k(f_k(...((IV))) \oplus m$, and ...
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Decryption considering AES OFB and ECB
I have the following pseudo code considering a ransomware methodology to encrypt files:
cFile = AESEncrypt(sessionKey, pFile, OFB, iv)
keyBlob = AESEncrypt(masterKey, sessionKey, OFB, iv)
ivBlob = ...
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OFB mode discussion
In OFB mode, I understand that a bit flip in $c_i$ for $i > 0$ only causes a bit flip in message block $m_i$. However, how is it possible for a bit flip in $c_0$ (i.e, in IV) will result in all the ...
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Who is the inventor of the OFB block cipher mode of operation?
Handbook of Applied Cryptography gives two resources for the OFB mode
1980 FIPS 81. This doesn't give any references, unlike NIST.
1983 ANSI X3.106, unfortunately pay-walled.
Who is the inventor of ...
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Is OFB-mode a stream-cipher?
I've seen that OFB is considered as a block cipher mode. But could we consider it also as a family of stream cipher?
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CTR and OFB block cipher modes and their post-quantum security. Some questions [duplicate]
It's said that quantum computers can break block ciphers with 2^(n/2) queries (being n the key size).
I read this paper: https://eprint.iacr.org/2016/197
It says that CTR and OFB modes are safe ...
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Does keeping the IV secret in OFB mode makes brute-force more complex?
If we keep the IV secret, does that increase the complexity of finding the correct key?
My first thought is that it increases complexity, but in real world, I can see that IV's aren't kept secret.
We ...
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does OFB mode has diffusion on the plaintext?
In some block modes, if we change one bit (or more) in the plaintext, the whole block\ciphertext will be changed (i.e ecb: block will be different. cbc: whole ciphertext will be different)
Does ...
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Known Plain Text Attack DES-OFB on Crack.sh
I am trying to do a known plaintext attack on DES-OFB through crack.sh. I have been having trouble lately. I keep getting blank text file back with no keys returned. Does anybody know if DES-OFB is ...
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OFB output jth-block expression clarification
Stalling says:
OFB encryption can be expressed as
Cj = Pj⊕E(K, Oj-1)
where
Oj-1 = E(K, Oj-2)
Some thought should convince you that we can rewrite the encryption
expression as:
Cj = Pj⊕E(K, [Cj-1 ⊕Pj-...
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How to encrypt small pieces of data (2 - 4 bytes) within Beacon advertising packet?
I'm developing a medical device that operates under extreme low-power constraints and transmits data with BLE, where every unnecessary millisecond of air time matters. I am developing a Beacon ...
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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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OFB mode vs LFSR
In the "Introduction to Cryptography: With Coding Theory" by Trappe and Washington, in the chapter about OFB (Output Feedback) mode the authors say that:
The OFB mode produces a bit stream and it ...
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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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Known Plain-text Attack [closed]
How can I find the known plain text P2 based on the given information? Assuming that the encryption is made using a common initialization vector and the mode used for encryption is OFB.
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How many bytes of the last keystream block are used to XOR the final block of partial plaintext in CFB, OFB & CTR modes?
I apologize if this is a dumb question but I'm trying to understand how the final block of partial plaintext is XORed using only n number of bytes in the final keystream block.
How do we determine ...
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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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What (if any) information can an eavesdropper infer in this scenario when using DES in OFB mode?
Assume that a company wants to use DES in order to encrypt messages
to remotely control its manufacturing machines. The company uses different
messages types of 8 ASCII characters length each. The ...
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What is the advantage of CFB over OFB?
I was wondering if CFB can be better than OFB in any ways. I would like to know in what cases one would use CFB over OFB.
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AES in OFB mode and IVs
I'm trying to understand cryptosystems and their implementations to understand how to properly implement them. I have a function implementing AES-128 in OFB mode. Let's call it
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OFB mode and CFB mode error propagation in 64bits
I am trying to understand (in simple terms), how error propagation works in the transmission of ciphertext in both OFB and CFB using a 64bit mode. I am having a hard time understanding the ...
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Security of OFB mode if PRP is used instead of PRF
In the cryptography lecture at my university, we had the theorem that (randomized) OFB mode is IND-CPA secure if the used pseudorandom function (PRF) is IND-PRF secure.
Afterwards, we investigated ...
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Is AES in OFB mode with same IV more robust than ECB mode?
I am looking at implementing AES128 bit encryption of a data stream. Since AES128 is a block cipher, which is inherently less robust than a stream cipher, I have considered configuring AES128 as a ...
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Does the Blowfish cipher work with OFB mode?
I'm trying to implement the Blowfish cipher in Output Feedback mode.
OFB mode has two operations, XOR and the block cipher. XOR inputs two blocks of the same length and outputs one block of the same ...
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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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Implementing 5 modes of operation with a hash function
Is it possible to implement any of the 5 modes of operation (ECB, CBC, OFB, CFB, CTR) with a hash function?
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What are the advantages of using OFB (Output Feedback Mode)? [closed]
I have a problem with OFB mode, because I have heard that it is stronger than CFB.
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Is MCrypt's 8-bit OFB mode secure?
I just stumbled across a Stack Overflow post which points out that the libmcrypt library (notably used in PHP) implements a somewhat unusual set of block cipher modes: it calls the usual CFB and OFB ...
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CTR_DRBG versus OFB_DRBG
As far as I know, in the development of ANSI X9.82, there was consideration of OFB_DRBG, a pseudorandom number generator based on block ciphers like CTR_DRBG, but it appears to have been rejected of ...
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With wrong IV at receiver side, the CFB in better than OFB?
Assume the receiver have a wrong IV (initialization vector), in the CFB mode only the first block of plaintext is wrong but in OFB mode the second and all blocks will be affected.
Is that correct? ...
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What's the advantage of using OFB/CFB/CTR modes over a stream cipher
As far as I understand:
The primary disadvantage associated with stream ciphers is the need for a random and unique key for each run in order to protect against reused-key attacks.
OFB/CFB/CTR block ...
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crypto design with AES-256 MODE OFB
I have the following APP Design
key store (contains 1:n user payload as 1:n key store entries)
key store salt (is used to extend to key store password to 256 bits, stored in clear text)
key store ...
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May the problem with DES using OFB mode be generalized for all feistel ciphers
There is a problem with using DES as the block cipher in OFB mode, eg: the feedback that goes back into the next round will be encrypted with the same key $k$ resulting back into the plaintext IV used ...
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How comparable is OFB to a one-time pad?
This is a rather trivial question, I just want to see if I get the concept right.
In OFB you generate a pseudorandom stream based on some nonce, and you XOR that with the message to get the ...
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Is the Blum Blum Shub PRNG suitable to create initialization vectors?
Is it a good idea to use a Blum Blum Shub Generator to create my initialization Vector (IV) in AES-OFB (Output Feedback Mode)?
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Probability of Repeated Encrypted Block In Output Feedback (OFB) Mode
Is there any probability/chances of repeated encrypted block in Output Feedback (OFB) mode?
Is there any existing documentation/studies about that? If it is existing, can you please provide me a link ...
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Capacity of Advanced Encryption Standard in terms of File Encryption
what is the capacity of AES in terms of File Encryption?
is it really good to encrypt a large files in AES? ex. I am encrypting a 8GB of File... is it still good to used AES?
is it still good to used ...
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Is my pseudo-random initialization vector secure?
How can I know if I am generating a secure pseudorandom initialization vector?
Currently I am planning to generate a pseudo-random initialization Vector using current date and time - is this secure ...
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Which attacks can be avoided by the use of OFB instead of ECB?
For a file encryption program, I was told to use Output Feedback mode (OFB) instead of ECB (Electronic code book) mode.
Which attacks can I avoid by this choice?
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Complexity of ECB and OFB
What is the complexity of ECB in terms of Time and Memory?
and also in OFB? I can't find it in the internet, so I decided to ask it in here.
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How does Output Feedback mode use the initialization vector?
How can I process Initialization Vector inside the Block Cipher Encryption box (using for example AES) together with the Key?
Will I encrypt the Initialization Vector like a block of plaintext?
So I ...
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Are CFB and OFB really meant for streaming?
CFB, OFB and other modes are meant for streaming and don't require padding. Are there still limitations such as the text needs to be greater than key length?
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