Encryption is the process of transforming plaintext using a cipher to make it unreadable to anyone except those possessing the key.

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How does one use AES block cipher modes of operation?

This is the sequel to my previous question about AES block cipher modes of operation. (See: AES block cipher modes of operation) Now, here is my real problem. I have to use a block cipher with 8 bit ...
3
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2answers
273 views

AES block cipher modes of operation

have a project in which I have to implement an en/de-cryption structure using a standard AES block of 128-bits in VHDL and I think I'm a bit confused. So I'd like to ask some questions about AES and ...
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1answer
285 views

WIN LM Password Hashes (using John the ripper) [closed]

In a problem set, we've been asked to use John The Ripper to crack a list of Win LANMAN passwords. They are of the following form: 953A55E36AB85C0B9DA92C18555E42E1:0169295E0A6A6B35B2DD9932D10C1978 ...
7
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2answers
323 views

Encrypting 8 times with 8-bit key beneficial?

I was trying to understand cryptography from the book Information Security by Mark Stamp and I am confused by something. Suppose that Alice has a secure block cipher, but the cipher only uses an ...
1
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1answer
123 views

Curve parameter for hyperelliptic curve cryptography?

RFC5639 defines some curve parameter for Elliptic curve cryptography. Aren't there any curve parameter database for Hyperelliptic curve cryptography? What I can only find was that written in this ...
2
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2answers
322 views

Can two rc4 encoded messages be XORed and decrypted if encrypted with the same key?

If I have the following: E1 = RC4(M1, K); E2 = RC4(M2, K); If two different messages M1 and M2 are encrypted with the same key, K, can the key be recovered by ...
0
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1answer
813 views

My encryption message system & question about security

I made this small tool for make & read easily an encrypted message without nothing to install, just a simple private key like a word or a couple of words to share. (Without say it directly of ...
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0answers
458 views

Decrypting a message without the private key using CRT

I am given 5 different encryption modulus, $N$, each ranging from 78 to 88 numbers long. Then for the encryption exponent, each has the same which is 5. Then I am given 5 different encrypted messages, ...
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2answers
154 views

Re-using parts of a one time pad to encrypt a new one?

The main problem with OTP's is the fact that they can only be used once. Would it be possible to use a random number that's, say, 512 digits, then use 256 of those for the (non-random) message, the ...
4
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0answers
136 views

Reordering non-block-aligned parts with DES in ECB mode

I was given a ciphertext file which was encrypted using DES in ECB mode. It is known that the plainttext that was encrypted has the following form: Each line of text consists of a payroll followed ...
4
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2answers
155 views

how to iteratively calculate a^emod n with modulus n sized 4096 bits

In most sites the exponent of the RSA public key is 24 bits. But the modulus can get to 4096 bits size. I have an accelerator that can get max. 2112 bit size modulus. It calculates ...
3
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3answers
537 views

Is public-key cryptography the only option in this scenario?

Two parties: a client and a server are to a agree on a symmetric key. Both the client and the server are aware of a master password. The way this is currently done ...
6
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3answers
2k views

Encryption/ciphers/codes in Chinese

I am quite curious as to how you can perform simple encryption for the Chinese language. Saw a similar question related to encryption/Chinese here: About cryptography in a character language, ...
6
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1answer
171 views

What does a “cycle” mean in cryptography benchmarks?

In this table of the "Crypto++ 5.6.0 Benchmarks", for example, cryptographic algorithm performance is measured in cycles per byte for symmetric ciphers, and in cycles per operation for asymmetric ...
28
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4answers
10k views

What are the practical difference between 256-bit, 192-bit, and 128-bit AES encryption?

AES has several different variants: AES-128 AES-192 AES-256 But why would someone prefer use one over another?
4
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2answers
334 views

Provable Encryption

Is it possible to encrypt data in a way that it can be proven that the data is encrypted, without revealing the key? Alice chooses some plaintext, then she encrypts it with a certain scheme. She ...
57
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10answers
4k views

Is modern encryption needlessly complicated?

RSA, DES, AES, etc. all use (relatively) complicated mathematics to encrypt some message with some key. For each of these methods, there have been several documented vulnerabilities found over the ...
2
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3answers
401 views

Using Whirlpool hashing function to encrypt data

I've read that the Whirlpool hash function can produce footprints that could be used as a pseudorandom generator. Is it "OK" to use it to encrypt some data using something like the following? ...
5
votes
2answers
481 views

What is the security loss from reducing Rijndael to 128 bits block size from 256 bits?

As you know in the past few weeks it has emerged that NIST/NSA have been involved in weakening encryption standards over a long period of time so that they can retain the ability to break encryption ...
6
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2answers
910 views

GPG symmetric encryption and javascript

I have a use case where I need to encrypt some text in the browser using javascript. Only the encrypted text will be stored on the server. The user should then be able to take the encrypted result and ...
3
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2answers
384 views

Are there public slow-but-strong algorithms out there that resist brute-force attacks better?

I'm reading that AES uses 4x4 bytes (4*4*8 = 256 bits key) matrix for performances matters (since it's a requirement for common standard encryption algorithms), but are there implementations with ...
4
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5answers
1k views

Is it possible to make time-locked encrytion algorithm?

I'm not sure if what I'm asking is even a valid question but here goes. Would it be possible to add a mechanism to an encryption algorithm that would mean it had to be a certain time of the day or a ...
3
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2answers
166 views

Using single EC cert/keying material to derive symmetric encryption key (for storage)?

The situation involves a single party (single certificate) who would want to AES encrypt a file that they can later decrypt. Assume the EC certificate + EC keys have a purpose i.e. "File encryption" ...
3
votes
1answer
155 views

How would I make a secret notation alphabet more secure?

Disclaimer: I was looking for a place to ask this question on SE and this site seems to be the most fitting. If this question doesn't belong here, feel free to redirect me. Just out of boredom and ...
4
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2answers
594 views

Order Preserving Encryption for Numeric Data Values

How can I ensure order of encrypted data i.e., Enc(m1) < Enc(m2) where m1 < m2, and all messages are integer values. I have gone through Order Preserving ...
3
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0answers
113 views

Which encryption method supports random reads?

I have a file containing 16-bit samples and I want to encrypt it, but the problem is that I need to be able to read any random 16-bit value from the file, and be to able to decrypt it, without reading ...
3
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4answers
268 views

Is it possible to anonymize web traffic so that the IP Address cannot be determined while still being able to determine distinct IPs?

I'd like to find a way to anonymize IP addresses in web logs to ensure user privacy given the following requirements: If given an IP address, there is no way to look up which requests came from the ...
1
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1answer
222 views

Why are the first few bytes of a gpg encryption always the same?

If I run the command 'gpg -a -e < input.txt > output.txt' with completely different inputs (e.g. from /dev/urandom), the first 19 characters are always the same. What is this header? Is it ...
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2answers
128 views

What are the weaknesses of this message exchange protocol?

Here is a protocol for a key exchange: Bob encrypts a message $m$ with his key $K_B$: $m_1 = E_{K_B}(m)$. Bob send the result $m_1$ to you. Alice encrypts my encrypted above message with her own ...
5
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1answer
545 views

Why is the P-521 elliptic curve not in Suite B if AES256 is?

In the NSA's document, "The Case for Elliptic Curve Cryptography", we have ...
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1answer
140 views

What are some of the major differences between PyNaCl and PyCrypto? [closed]

It seems like one can generate keys and encrypt data with both libraries. Is one better than the other? Do they attempt to solve different problems? Is one more secure than the other?
2
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2answers
294 views

Is there an encryption/decryption algorithm that can give two different outputs?

The recent revelations that airport staff can detain travellers in an interrogation room and force them to give over passwords to encrypted-HDD laptops under threat of jail time has made me think ...
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2answers
367 views

RSA PCKS1 v2.1 RSAES-OAEP algorithm

Using RSA public key (n,e) the encryption of a message is c= (m^e) mod n and the corresponding message is decrypted as ...
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1answer
212 views

Encryption schemes and pseudorandom permutations

Can an encryption scheme (deterministic or not) be viewed as a pseudorandom permutation taking as input a message and returning a value of the same bit-encoding length ? Thank you.
7
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3answers
208 views

AES CTR with similar IVs and same key

Lets say there is a piece of software that uses AES CTR to encrypt different messages using the same key but with slightly different IVs So for example, a 16 byte IV, the 2nd 8 bytes are always the ...
1
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4answers
821 views

Initialization vector in symmetric-key encryption

Can we use symmetric-key algorithms without an initialization vector? I am making an app where both the sender and receiver share a key and there is no way to create an initialization vector for each ...
2
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2answers
121 views

Storing Credentials for a Third Party

(Originally posted to SOF, but I got no answers) I am designing a small application for use inside my company. My application needs to connect to a third party website on behalf of my application ...
3
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2answers
175 views

Is there a cryptographic function or system in which it becomes HARDER to break as time passes?

Is there a function or system which is time depending in which the effort required to brute force the decryption increases with time? It is easy to break encryption from many years ago because ...
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0answers
38 views

How does a cracker know if they've broken AES-CBC encryption? [duplicate]

How does a cracker know if they've broken CBC or stream encryption? With hashe cracking one would know because you have the password that you started with to test. But for CBC decryption, you have a ...
4
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1answer
157 views

Why no swapping block in the last round of DES?

Round 16 on the encryption side, and round 16 on the decryption side of DES have no swapping module. Why is it like this? Can anyone provide any justification? This is my homework question.
6
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4answers
241 views

Is there a public key encryption scheme with optimal key size?

Symmetric encryption schemes such as AES have known security levels equal to their key sizes (i.e. breaking an encryption with an $n$ bit key needs about $2^n$ work steps). Elliptic curve encryption ...
6
votes
1answer
584 views

Is AES-XTS considered safe to encrypt multiple files with the same keys?

I was wondering if changing the cipher mode to AES-XTS in EncFS would be a sound idea. EncFS uses AES in CBC mode until the last 1KB block, and CFB mode for the last block if ...
5
votes
1answer
159 views

What does ''latency'' really mean when a block cipher is partially unrolled?

Typically,I think latency should mean the time from the first plaintext input to the first ciphertext output, when the block cipher is not totally unrolled (such as AES unrolled with 2 rounds). If I ...
2
votes
2answers
104 views

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 ...
2
votes
2answers
136 views

No IV for one off symmetric file encryption

My question is (hopefully, for somebody) a simple one; but my project is holding as I'm not sure. I read on SO that generating encryption keys without an IV is a bad idea, so is using a constant IV ...
3
votes
2answers
350 views

Encrypted counter as IV in CBC mode encryption using same key

I'm currently working with a secure transport protocol that defines the IV to be a counter (incremental nonce) to be encrypted with the same key. This is a followup to a protocol that did not provide ...
2
votes
3answers
146 views

Secure communication between multiple peers on a public channel

I am wondering how can I secure communications between multiple peers over a public channel, like an IRC channel. With two peers it is easy - they exchange their encryption keys and decrypt the ...
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1answer
64 views

The specification of modern, non-communicating cipher machinery [closed]

I'm looking for references, papers or guidance on a class of system which I have not seen widely discussed. Consider powerful electronic machinery which remains in the custody of communicating ...
2
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1answer
132 views

Multiple parties must encrypt and get the same result

Hopefully this question is not too simple - I did some research but with encryption I really don't want to make a mistake. Our scenario is that multiple groups need to encrypt a number and arrive at ...
0
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1answer
178 views

Is the salt value a secret or can it be stored in cleartext just like the IV? [duplicate]

From Wikipedia I read that the IV is used to randomise the mapping of cleartext to cipher text and that the IV is usually stored (in cleartext) together with the encrypted record. ...