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1

For encrypting data, it's generally recommended to store a random key and encrypt this with the appropriately salted password. This means that if/when the user changes their password, you only need to decrypt and re-encrypt their key, and not all their data.


4

Do not use SHA256 to hash passwords. SHA256 is a message digest algorithm. It is designed to be very fast. Use an algorithm which is intentionally designed to be slow and hard to implement in specialized hardware. Why? Because fast algorithms allow an attacker to brute-force a large number of passwords until they found one which works. "They'll still have to ...


3

it depends, but - generally - no. AES is a block cipher, so you're breaknig a thing by 256 bit blocks in your case. And 100KB is more than enough to guess a type of "what's inside", by MIME, for example, after that a task is a way more simplier


0

I think the reason for the downvotes is that the result of a file encryption is a new file. Consider this example: openssl enc -aes-256-cbc -in $HOME/somefile -out someEncryptedFile.enc In a command line, this would tell openssl to encrypt somefile and output someEncryptedFile.enc. You can choose the name for your output file however you want. I ...


1

I realize the post is from 2013, but I happened upon this post when researching a patch for the latest openSSL vulnerability announced 3 May 2016 (Info - https://www.openssl.org/news/secadv/20160503.txt). The recommended patch is TLS1.2+AES-GCM cipher suite. The latest browser on the latest OS should have support for AES-GCM at this point. If you'd still ...


3

This is actually a quite tricky problem with no perfect solution. If the file system was one were data is written only once and written entirely sequential, a single CBC encryption all the way from the start of the media to the end would be suitable. You can do random access decryption of CBC, you just need to read one additional cipher block. This could ...


3

The IV has the same security requirements as the encrypted blocks. For CBC to work, you need to XOR the unencrypted data in the current block with the encrypted data from the previous block. Because there is no block before the first block (so no encrypted block can be obtained) an IV is used instead.


5

All modern encryption methods (AES, blowfish etc.) are designed to be much more secure than you seem to expect. Let us quickly look at some attacks which such ciphers are designed to be resistant against. Known plain text attack - In this case we assume the attacker has access to many plain text blocks along with corresponding cipher text blocks encrypted ...


24

I think it's easier to split this into its component parts, and consider them as separate entities: AES and CBC. AES itself does not "basically consist of XORing together chunks of the block" - it's a much more complicated affair. Ignoring the internals of it for a moment, AES is considered secure in that without knowing the key, it's practically impossible ...


-4

The Initialization vector used is a random number also called nonce which when combined with a secret key makes the original data completely unreadable. The data when first XOR with plaintext data, it randomizes it. Additional secret key encryption will make it even more harder to read. Hence IV essentially need not be secret since the encryption with a ...


8

No, because the key is secret. The "block cipher encryption" block in the diagram scrambles the data depending on the key. The XOR in the diagram does not provide the security, the encryption does. The XOR and the IV are just to make sure the same plaintext encrypts as different ciphertext for each block.


0

To answer your question: Yes. You are facing two problems: 1) ECB is inherently unsafe to use and is only meant to be used as a building block for more safe operations. ECB mode produces the same output for the same input each time so it is extremely deterministic. 2) Because of the properties mentioned in 1 it will become trivial for an attack to ...


9

For hash functions (like SHA-1) being used to sign SSL certificates, the security is completely undermined if you have successful collision attacks. Due to the birthday paradox, a N-bit hash function effectively provides about N/2 bits of security against collision attacks. That is a brute-forcer can create collisions for a N-bit hash function after ...


5

AES is a symmetric encryption algorithm. SHA-1 is a hashing function. They are completely different beasts. The issue is not the number of bits but the functions themselves. As an example you can take MD5. It also has 128 bits, yet creating two colliding strings is now trivial. The issue is not being able to bruteforce the 128-bit possibilities, but ...


2

DPAPI stores protected data encrypted with the user's DPAPI key, which is in turn encrypted with a derivative (via PBKDF2) of the NTLM password. Furthermore, the DPAPI-related key information is stored in a protected memory region within the security subsystem (LSA), making it particularly difficult to compromise the master keys outside of an administrative ...



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