Questions tagged [cfb]
Cipher Feedback Mode (CFB) is an encryption mode, that builds a self-synchronizing stream-cipher from a block-cipher.
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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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Figure out chosen-plaintext-attack in Zerologon attack
Actually, I'm reading the description about Zerologon attack from the original whitepaper document. In there, Tom Tervoort mentions these sentences:
So I tried to come up with some chosen-plaintext ...
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Full-Block Cipher Feedback Mode as a complete AEAD with a free MAC?
Full-State Keyed Sponge (aka Donkey Sponge) appears to cross over into block cipher mode territory such as Full Block Cipher Feedback Mode:
Full State Keyed Sponge (FKS) construction:
FKS has been ...
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Recommended way to generate a key and IV for CFB mode?
I need to generate a key and IV that will be used to encrypt multiple things over a period of time with AES in CFB mode. The decision to use AES in CFB mode is not mine to change and the key will only ...
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DES in cipher feedback mode CFB
We use DES in cipher feedback mode (CFB) to encrypt a plaintext $m = m_1\mathbin\|m_2\mathbin\|\ldots\mathbin\|m_{100}$ into a ciphertext $c_1\mathbin\|c_2\mathbin\|\ldots\mathbin\|c_{100}$, where ...
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Modification of CFB Mode of Operation?
To encrypt plaintext $(P_1, P_2, P_3, ... P_n)$ Ciphertext Feedback Mode (CFB) works as follows :-
$$
C_0 = IV \\
C_i = E_K (C_{i-1}) \oplus P_i
$$
Lets define a modified version of CFB mode as ...
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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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Why does CBC-MAC(M) = CFB-MAC(M)?
I don't understand why $\text{CBC-MAC}(M) = \text{CFB-MAC}(M)$. Has it something to do with $\text{CBC-MAC}(M) = C_L$ and $\text{CFB-MAC}(M) = E_K(C'_{L-1})$?
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Is using CFB in SIV secure?
Is SIV mode variant equally secure, if you replace CTR mode encryption with full-block CFB mode encryption?
CFB seems to be safe with predictable IV: Is using a predictable IV with CFB mode safe or ...
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does CFB support random read access?
According to Wikipedia block cipher modes of operation, simplified CFB supports random read access. but what about the real CFB where we have a shift register? below are pictures extracted from the ...
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Block Cipher Mode of Operations
I am studying for a test and I don't seem to understand the Block Cipher and its different modes of operations especially when it comes to encrypting and decryption. Could anyone please help solve ...
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What is the difference between cfb and cfb1 and cfb8 ? ( like openssl's aria-128-cfb & aria-128-cfb1 & aria-128-cfb8 )
What is the difference between cfb and cfb1 and cfb8 ? like openssl's aria-128-cfb and aria-128-cfb1 and ...
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Struggling to understand CFB mode (with DES)
I'm really struggling to understand CFB mode (with DES if that matters). I realise after searching around here that these modes are now obsolete but I need to understand them for class. From wikipedia,...
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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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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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Security of CFB on a public channel
Given a server that broadcasts all received data to all connected peers (except the sender), two participants can have an encrypted conversation using a self-synchronizing method like CFB and some ...
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Cipher feedback mode with shift registrers
Can someone please explain to me how the Cipher Feedback Mode works? From what I have read some examples have a shift register in its explanation but some examples don't. Is there two versions of CFB ...
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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 this a secure method of encrypting with authentication?
My goal is to allow two clients to send files securely over an untrusted network without the need for more than one block of information to be sent. Both clients have ECDSA keys of size 256 bits. I'd ...
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Self-synchronizing cipher recovery from dropped bits
This cryptography book says:
There are also asynchronous or self-synchronizing stream ciphers,
where the previously produced ciphertext bits are used to produce the
current keystream bit. This ...
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Cipher Feedback Mode
I can't understand what CFB really is. It said in Wikipedia that CFB is same as CBC, but I find that CFB is more difficult than CBC.
Can someone explain to me how CFB works. Such as how ...
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64 bit clock cipher with CFB mode. One-byte defected from ciphertext. What is the number of bits defected from plaintext
I have a question from an exam;
We encrypted a message of size 100 Bytes with CFB. In the transmission, byte number 12 got defected. How many bits defected will be in the decryption. The answer is 72 ...
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Encrypting text using Caeser cipher in CFB mode
I am interested in learning and understanding cryptography and its application in every day life. One thing I can't seem to get my head around is encrypting plaintext using a block mode such as CFB. I ...
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Cipher Feedback Mode - sizes of the blocks and shift registers
I have a question regarding the resulting sizes of the blocks and shift registers in Cipher Feedback Mode.
In the web there are different pictures to illustrate the CFB-mode.
Now on the first ...
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How do I check if the output of my CFB TEA encryption algorithm is correct?
I have an assignment question regarding the TEA cipher in CFB mode. After much difficulty and research, I managed to produce an 8-bit TEA / CFB encryption algorithm. My input is supposed to be a ...
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3DES CFB vs CFB8 modes
What is the main difference between CFB and CFB8 modes in 3DES? Is it only a change in block size from standard 8 byte to 1 byte when doing 3des and XOR? I cant find any pseudocode for this CFB8 mode?...
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Show number of affected blocks using CFB DES decryption of altered ciphertext
I have encrypted a file using -des -cfb and now I want to view how many blocks it contains once I decrypt it.
I have done this on the Linux terminal. I know that 9 ...
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8-bit CFB in DES and AES - error propagation
I have two questions for an assignment that I need to answer in relation to Error Propagation in 8-bit CFB mode for AES and DES encryption. The questions are as follows:
If there is an error in ...
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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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How to encrypt a short plain text?
I want to encrypt a short plain text (i.e., 30bit), and the requirement is that length of cipher text is the same as the short plain text.
It seems that stream encryption methods like CFB-8 ...
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requirements for CFB encryption mode
In my course there is a remark saying that in CFB encryption mode, the plaintext must not a multiple of the block length.
Why?
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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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Why are ECB CBC and CFB parallelizable?
I guess I do not understand the word 'parallelizable'. Why are ECB CBC and CFB parallelizable?
It would be nice if someone could explain it in a short way.
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Number of cycles in cipher feedback mode (CFB)
How many cycles are there in a CFB mode of operation?
Say for example I use AES encryption in CFB mode. How many times will this cycle before outputting the final ciphertext? In the picture below ...
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CFB-Mode biterror
By definition of self-synchronising cipher, if part of the ciphertext is lost (e.g. due to transmission errors), then the receiver will lose only some part of the original message (garbled content), ...
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Is it possible to decrypt the 2nd byte of AES-256-CFB-8 ciphertext without decrypting the 1st byte?
I am stuck with AES-CFB decryption.
Assume I encrypted plaintext helloworld (10 bytes) using AES-CFB.
Now I want to decrypt the second byte ...
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Break AES-CFB mode having access to a AES-CTR black box
I need help for a "simple" problem
Let's suppose an intercepted ciphertext C encrypted with an AES-CFB mode of operation, using key K and some IV (IV is probably at the begining of C)
The system let ...
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For CFB, if the IV is corrupted, can the system re-synchronise?
How does CFB (Cipher feedback mode) self correction work? And if the initialization vector (IV) is corrupted during transmission, how will it affect encryption or decryption?
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Is a chosen ciphertext attack on PGP still possible?
In a paper from 2002 (pdf), Jallad et al describe a chosen ciphertext attack on PGP by taking advantage of the CFB mode that the block ciphers use under PGP. It's quite a devastating attack.
Is this ...
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What is the benefit of artificially padding messages? [duplicate]
For ECB, CBC, and CFB, padding is required when the plaintext does not fill out a complete multiple of the block size. However, I have heard that is good practice to pad all messages, even if the ...
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Where is CFB-MAC defined?
I can find descriptions of using CFB mode to create a MAC and even implementations, but cannot find any standard or papers analyzing its security bounds.
Is there a standard for CFB-MAC?
Where can I ...
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Making both the IV and salt public for PBE with AES-CFB
Is it okay to make both the IV for AES-CFB and the salt for PBKDF2 public? Does this action of mine compromise security in any way?
I have an implementation of this cipher and had previously asked a ...
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Is it secure to use ciphertext feedback with RC4?
Consider the following modification of RC4 to give some "ciphertext feedback"
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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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Can CFB mode of block cipher be used as a commutative encryption?
Can CFB mode of block cipher be used as a commutative encryption?
Is it possible to use CFB mode of AES block cipher to create commutative encryption?
With CTR it is possible but not secure.
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Parallelization of CFB mode encryption and decryption
While reading Evaluation of Some Blockcipher Modes of Operation by Rogaway (someone just linked it somewhere), I noticed two claims about CFB that I'm not sure I understand:
Regarding whether CFB ...
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Is using a predictable IV with CFB mode safe or not?
While writing this answer, I noted that NIST SP 800-38A says that (emphasis mine):
"For the CBC and CFB modes, the IVs must be unpredictable. In particular, for any given plaintext, it must not be ...
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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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How openssl padding for AES cfb IV?
From a few documents I have read and a few questions about padding here, I think if I passed a encrypted text fewer than BLOCK SIZE, openssl would pad it per PKCS7. And use that padded encrypted text ...
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How does ccrypt work?
On many Linux/GNU distributions CCrypt (ccrypt) by Peter Selinger is available as a command line utility to encrypt files. How does the protocol work and is it ...
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