ways of applying a block cipher to multi-block messages and enabling repeated use without changing the key.

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Reykeyed AES in CTR mode as a stream cipher

Suppose one uses AES in CTR mode to generate a keystream, but every $l$ bytes the $n$ bits that would follow are used as a new AES key. Assuming that AES is a secure PRP: Is this a secure stream ...
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28 views

Does extra encryption improve the security of CBC and CTR?

I am learning about cryptography and during my research and reading I had a question. When looking at information leakage and CBC mode, I asked if there is a way to improve this with by using the ...
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39 views

Is this a better GCM?

Using the keystream from the block cipher for both parts of the GMAC key (initialization and encrypting the auth tag) seems to produce a better mode of operation than GCM, as successful forgeries and ...
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58 views

Does not using padding mean a lack of security?

I've read several texts which say that if the entire plaintext is a multiple of the block-size padding is not required (and not using padding would not mean a loss of security). I generally disagree ...
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446 views

Non-malleable file encryption using AES XTS 256?

I'm looking to do file encryption of a bunch of individual files, some small, some quite large. The files will be write-once/read-many, so I could use CBC, however, since the read-access needs to ...
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2answers
329 views

mode of operation in cryptography

We need to choose a mode of operation for a Telnet like application where the average message size is between 7 and 1024 bytes. What is the best mode of operation in this case? a. CBC b. CFB c. ...
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467 views

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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97 views

Are modes of operation algorithms practical?

I took a cryptography class back in college, and now that I am working my 1st career one of the things currently on my plate is coming up with an algorithm to encrypt data before it's placed on the ...
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1answer
50 views

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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281 views

Operation modes of block ciphers how are used?

I am studying about different operation modes of block ciphers my question isn't something specific to that, but is how these operation modes are used in cryptography? I have this picture here ...
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1answer
240 views

Block cipher mode with diffusion on ciphertext

As I understand, diffusion property in AES-CBC ensures that one-bit change in plaintext will yield changes in all following blocks in ciphertext upon encryption. I'm looking for algorithm that will ...
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2answers
113 views

Counter Mode with a sequence of zeros bits plaintext, is it secure?

I had a quiz last week in computer security course. There was a confusing question that I am still looking for a good and clear answer. First, I know that counter mode with a good block cipher is ...
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2answers
535 views

IV/Nonce in CTR&GCM mode of operation

We know reusing IV can compromise our secrecy. I have some questions aiming to clarify the use of an IV/Nonce in CTR/GCM: Is it OK to use the same key for encrypting plain-texts in authenticated ...
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1answer
77 views

what problem happen if we always use IV Zero in CBC Mode? [duplicate]

i have a question about CBC operating mode. what problem happen if we always use IV Zero in CBC Mode?
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1answer
230 views

Why using AES in ECB (Electronic Code Book) mode a bad idea? [duplicate]

Why using AES in ECB (Electronic Code Book) mode a bad idea? is CTR mode better? Given only these two can be used for parallelization.
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18 views

Is it okay to use Threefish-512 in ECB mode with Poly1305 MAC to protect some AES keys?

A person has some independent AES-GCM-SIV keys they need to protect as part of a hypothetical protocol or product, where it is publically known that it is in fact AES-GCM-SIV keys that are being ...
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38 views

Is it possible to create a detection oracle for all block cipher modes? — ciphertext-only cryptanalysis

I have made an ECB/CBC detection oracle, and am now trying to make a detection oracle that can differentiate between CBC/CFB/OFB/CTR/etc. I can already tell ECB apart from the others due to this ...
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40 views

Why we use operating modes in cryptography? [duplicate]

Why we use operating modes (CBC , . . ) in cryptography? i mean what is the essential of use it ?
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1answer
151 views

Which block cipher mode does the experts use? [closed]

I want to know which "block cipher mode of operation" does the experts use? I don't want to use ECB or CBC because add padding and padding mess up my code. So which one does the experts use. /Thanks ...
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1answer
206 views

What's the best packet cipher mode for use with UDP for example? Advantages or disadvantages of any alternatives?

Cipher modes typically assume data is streamed or read from a reliable channel with guaranteed ordering. However, many communication transports, such as UDP, are not reliable and don't guarantee order ...
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1answer
547 views

File Encryption/Decryption in ECB mode [duplicate]

Possible Duplicate: Removing Padded Value in Decrypted Message I tried to encrypt and decrypt a file in ECB mode using AES Algorithm but I encountered one problem during decryption, I don't ...
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1answer
89 views

Which Block cipher mode should I use? [closed]

Which of the Block cipher mode is MOST secure? I dont care about the performance just the most secure