Questions tagged [cfb]
Cipher Feedback Mode (CFB) is an encryption mode, that builds a self-synchronizing stream-cipher from a block-cipher.
57 questions
0 votes
1 answer
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AES 128 CFB : first decryption from initial IV OK, issues from second
I'm making documentation for an ethernet gateway that using Lantronix xPortEDGE module. It can encrypt/decrypt in AES 128, 192 and 256 bits. I'm struggling to get more information from the ...
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0 votes
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112 views
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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2 votes
2 answers
260 views
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 ...
1 vote
0 answers
652 views
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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1 vote
0 answers
73 views
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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8 votes
1 answer
1k views
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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3 votes
1 answer
210 views
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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2 votes
1 answer
159 views
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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5 votes
2 answers
426 views
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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3 votes
1 answer
639 views
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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2 votes
2 answers
288 views
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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0 votes
1 answer
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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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0 votes
1 answer
733 views
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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1 vote
0 answers
340 views
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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0 votes
1 answer
78 views
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 ...
