Questions tagged [cbc]

Cipher block chaining (CBC) is a method for encrypting large amounts of data with a block cipher that can only encrypt fixed length plaintexts. When used with an unpredictable initialization vector (IV), it is secure against chosen plaintext attacks (CPA-secure).

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AES CBC Security

I am building an Apache webserver with TLS 1.2 and OpenSSL 1.0.1. So far, I have enabled 2 encryption algorithms - ECDHE AES256 GCM and ECHDE AES128 GCM. Firefox and Chrome(ium) use NSS which ...
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Why not use CBC, not send IV, and assume first plaintext block is garbage? [duplicate]

Possible Duplicate: Using CBC with fixed IV Forgive me if this has been asked before, I looked but haven't seen any answers that suit. Is there any danger in using CBC, encrypting a message plus ...
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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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Is the 1st Encrypted Block Less Secure Than Subsequent Ones?

It's my understanding that Electronic Code Book (ECB) produces similar cypher text for similar plaintext inputs which is not a good thing. To get around that, Cypher Block Chaining (CBC) can be used ...
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Secure Hash Function based on AES

How secure would a hash function be which appends an extra block of 16 zeroed out bytes to the end of the message and then AES-encrypts it with a well-known password (say the first 128 bits of pi) ...
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ECB vs. CBC, I've seen the pictures, but what's the actual strength difference?

I hope that this is not a duplicate because I'm looking for nuance. I understand the difference between ECB and CBC for a block cipher, and I understand that ECB is susceptible to replay attacks, but ...
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How resilient to attackers with extreme resources available is this encryption method?

How could the following scheme be made more resilient to attacks capable of utilizing massive amounts of resources? Assume all random values are cryptographically secure. Key derivation: scrypt ...
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Which block cipher mode to use?

I am working on securing a chat application, and I am not sure about which block cipher mode I should use. I am aware that I should avoid ECB as it's insecure, but what about CBC? I have watched ...
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Initialization vector length insufficient in AES

I use AES with AES/CBC/PKCS5Padding with the following encryption and decryption code sections in Java: ...
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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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Is there a form of AES encryption where the cipher text matches the length of the clear text and does not show patterns?

I have clear text, usually less than 10 bytes, which contains a few infrequently changing bytes. Reading: http://lollyrock.com/articles/nodejs-encryption/ I tried ...
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using hash function of (key||plaintext) instead of random value for IV

for a protocol which implements AES under CBC mode, an $IV $(initialization vector) is required for each encryption. Instead of picking the $IV$ randomly, is it advisable for us to set the $IV$ to be $...
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Is CBC theoretically harder to brute force when compared with ECB?

Theoretically – is CBC mode harder to bruteforce when compared with ECB when assuming: we ignore computational cost for the XOR operations, and the IV is made public?
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What are the implications of XORing ciphertext with plaintext?

I was intrigued by this question: Does adding complexity mean a more secure cipher? And it led me to wonder: What are the implications (if any) of XORing a ciphertext with the original plaintext ...
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With DES, is ECB encryption mode equivalent to CBC with null IV for short data blocks?

I got to this by experimentation, but can someone maybe provide an explanation for this?
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Cipher Block Chaining Ciphertext Alteration

I am new to cryptography. My professor's slides say that "Disadvantage: altered ciphertext only influences two blocks" for the CBC. However, since we xor the ciphertext from the previous block and the ...
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Is the output of AES-CBC + MAC the same size as the input?

I use AES-CBC and HMAC-SHA256 to encrypt a text file. Will the output be larger in size than the input or will it be the same size? Is it more secure secure if the size of the output is larger?
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Encrypting firmware with AES and no IV [closed]

I have an embedded device with a AES CBC engine on it that is used to ensure the integrity of the firmware. I know that CBC mode requires unique IVs to be any good, but I'm unsure if it makes a large ...
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How do I calculate the maximum plain text length allowable for a certain cipher text length?

I am encrypting and storing sensitive values in the database. I have a set max length in the database, but in order to provide useful user feedback, I'd like to know the max input I should allow for a ...
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Cipher Block Chaining - How do you change the plaintext of all blocks?

I've just read about CBC encryption and decryption and was wondering how you can change every plaintext block? Let's say you have an initialization vector, 3 ciphertext blocks, know each block-cipher-...
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Plaintext Size Limit for ECIES with AES-128 CBC mode

Using the ECIES (Elliptic Curve Integrated Encryption Scheme), is there a limit size of plaintext? (what is the maximum allowed number of bytes to be encrypted with ECIES).
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How is a PRP different from PRF? Both can be inverted to get the same input

PRP is said to be a bijective function which means that there is a one-to-one mapping with the output. And hence the output can be inverted using the decryption algorithm to get the same input. ...
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How to provide partial confidentiality and full integrity for a protocol message?

I want to provide confidentiality and integrity for a protocol. I don't want to encrypt the entire protocol message. I do not want to encrypt the header and timestamp of the protocol message, but I ...
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Is CTS necessary on a AES-CBC DRBG?

As I understand it, CTS pads the last block and swaps it with the second last to compensate for a partial block of data. I have written a DRBG (Deterministic Random Bit Generator) using AES-CBC that ...
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Decrypt AES-128 with key file but missing IV? [duplicate]

I want to decrypt a file that has been encrypted using AES-128 in CBC mode using OpenSSL. I got the “.key” file – which is 32 digits – but when I try to decrypt with OpenSSL, the program asks me for “-...
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Is it worth applying a MAC on data in a HSM?

I'm building a basic HSM out of an Arduino, and am using the following scheme to store data: Master symmetric key $k_m$ stored in firmware (secure bit set to prevent trivial extraction). Secondary ...
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754 views

CBC related TLS cipher suites to be disabled in the server side

I understand the TLS cipher suites using CBC mode are susceptible to timing attacks. From that understanding it seems that the cipher suites using GCM (CTR-based) are safe to use considering they don'...
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Decrypting an encrypted aes 256 cbc text with random IV, decrypts the string [duplicate]

This may be a basic question but bear with me. I started encrypting a text with aes 256 cbc mode generating a random iv of 16 bytes and a key. ...
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Cipher Block Chaining (CBC) encryption in SSL

Is cipher block chaining (CBC) mode used in SSL encryption? If block reordering is already protected by SSL and TCP sequence numbers, what added advantage does CBC provide?
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CBC Mode error during encryption

In CBC mode I know that if i get a corrupted Ci* block than Pi and Pi+1 will be wrong during the decryption, but i believe that this happens only when Ci* is not envolved during the feedback stage at ...
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Cut through mode for TLS AES-CBC / SHA ciphersuite

I am looking at RFC5246 and it seems that AES-CBC/SHA cipher suites cannot be implemented in a cut-through mode. Let's suppose that received record spans two segments. As i understood HMAC ...
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Security of AES counter mode vs. CBC mode

For AES-CBC to be CPA secure the IV that is used has to be randomly selected for each packet. If the IV is predictable than the encryption is not CPA secure. Is the same true for AES-CTR mode? that is,...
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CTR vs CBC cycles per byte with OpenSSL EVP

I did some benchmarking using the EVP calls of OpenSSL in C, for CBC and CTR encryption/decryption. (1) : I got 3.2 Cycles/Byte for CBC encryption. (2) : I got 0.7 Cycles/Byte for CBC decryption, CTR ...
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Data decrypted, but unwanted characters in the beginning

I am a bit new at cryptography, I tried to recover data from an old app database, I got the key and the type of encryption, it says "AES/CBC/PKCS5Padding", I used this online tool http://8gwifi.org/...
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security of design for sending files

let's say I have a protocol to send a fi le $F$. I am intending to employ AES in CBC mode for encrypting $F$ where the $IV$ is randomly chosen. For authenticity, I am employing $HMAC$ to compute a ...
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Disk encryption using AES-CBC: is reliance on previous block data a downside?

I have seen drives that boast that they use AES with CBC mode, which doesn't really make sense in my opinion, sure it's more secure than ECB (but actually, leaving security aside, ECB is better suited ...
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Is it safe to use AES-CBC like this?

Is it safe to generate the IV for AES-CBC as the following? It's like the real IV is all zeros. The first block of data will be a low-entropy but unique data. Once the first block is encrypted, the ...
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Padding size with a CBC Block cipher in TLS

I'm currently looking at an encrypted Client Finished message in Wireshark from a TLS session. The cipher suite that was agreed on in previous messages was ...
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Session based AES with random key and static salt

I'm currently using aes to encrypt/decrypt messages to and from a web service. When the user establishes a session he sends a random generated secret via rsa public key. This secret is used to ...
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AES CBC MAC splicing attack

I'm trying to implement AES CBC MAC splicing attack in Python, the idea is: given a message M, its tag Tm (MAC(M) = T), a new message N and its tag Tn we build a message such as: M||N = (M1, ..., Mn, ...
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Use of CBC-AES-256 to encrypt usernames

I came across some code in our project that encrypts usernames (limited to 50 chars, most are less than 10) using the following parameters: IV size is 16 bytes Key size is 32 bytes Algorithm is CBC-...
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AES-256-CBC with random IV - storing same plaintext as same ciphertext

I am encrypting some information stored in a column of a MySQL database. The column can contain repeated values, let's say the table has 7 rows and the column to be encrypted has the following values:...
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Decrypt simple CBC with XOR

I have searched and my problem is exactly the same as shown here: Decrypt simple CBC message with known IV using XOR encryption However, when I implement the solution it doesn't work, neither does ...
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Is AES-CBC mode not secure against chosen cipher-text attacks even if the IV is not predictable?

I've seen questions where people have asked if AES-CBC mode is vulnerable to chosen cipher-text attacks if the IV is predictable. But is it guaranteed to be secure against chosen cipher text attacks ...
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When using AES-CBC-128, what attacks become feasible as you decrease the entropy of the IV?

16 bytes is the recommended entropy for the IV, AFAICT. Is 12 bytes of randomness with 4 fixed (across invocations of this encrypt function) bytes at the end, significantly worse? How so? What about 8 ...
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Difference between XORing the IV and just pre-pending it to the plaintext before encryption with AES-CBC [duplicate]

The normal way of using AES-CBC is to XOR the IV with the first plaintext block This way you have to pass the IV along the ciphertext. What if instead of XORing we just put a fixed size randomIV in ...
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Is double AES-CBC encryption with the same key and IV unsafe?

If some plaintext encrypted twice with the same AES function (CBC-mode), same IV and same key, is it possible to retrieve either the key or the plaintext?
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Question about Cipher Block Chaining(CBC)

I'm studying at the moment the CBC Encryption method,and I was asked in an excercise how many bits would be wrong after decryption if during the transmission 2 bits are interchanged. My guess is that ...
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Is it safe to use the same IV for multiple encryptions in AES CBC mode when you are always encrypting random bytes?

I am generating random bytes (16 or 32 bytes at a time), and I want to encrypt them using a 128 bit AES key in CBC mode. Am I really weakening this horribly if I am reusing the same IV and key each ...
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AES128 Decryption in Objective-C just slightly off

I have been asked to integrate a home-grown CRM system with a 3rd-party data service provider (DSP). The DSP has encrypted the information they are providing. I only have their decryption ...