Cryptography Stack Exchange
Cryptography Stack Exchange

Questions tagged [ofb]

Output Feedback Mode (OFB) is an encryption mode, that builds a synchronous stream-cipher from a block-cipher.

Output Feedback Mode (OFB) makes a block-cipher into a stream cipher by generating a keystream using the block-cipher that is XORed with the plaintext to produce the ciphertext. OFB mode feeds back the raw output of the block-cipher as the next input of the block-cipher to create successive keystream blocks.

See the wikipedia page for more information.

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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 the OFB mode of operation?
kelalaka
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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?
m33lky
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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. When implementing the AES cipher encryption side,…
juhist
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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 initialization vector as a custom HTTP header is considered…
Lucas
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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?
Malexc
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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 stream cipher in OFB mode as shown here. If I use…
mr_js
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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 cipher modes turn the cipher into a stream…
krkhan
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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 mathematical concepts put into simple terms. Thanks.
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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)?
goldroger
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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 AES-OFB in encryption of large files? What also…
goldroger
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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 enough? If the answer depends on the block cipher…
goldroger
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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 modes, with full-block feedback, "nCFB" and "nOFB"…
Ilmari Karonen
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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 attacker can figure out the encryption function…
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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?
Ievgeni
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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 encrypts similarly to the LFSR(Linear-feedback…
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