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-1

In order to stop speculations, decrypting altered encrypted file using AESCrypt results in 'Message has been altered and should not be trusted' dialog box coming from reliable HMAC computation and is forbidding decryption. The software is also using random salt, contrary to VSEncryptor, for example.


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The "key expansion" or subkey generation in AES is an iterative process. Due to some work I am doing about this block cipher I have prepared an figure that may help you: The algorithm is checking if the iterator of the generator is in congruent with 0 modulo #columns to proceed with 3 operations or only with one if is not. The rotWord() is a circular ...


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Can I say that 128 bit using AES provide more security than 1024 using RSA? Yes. The effective security provided by AES-128 is approximately 126-bits due to some reduced rounds attacks on AES. That is, it lost a couple of bits of theoretical security. The effective security provided by 1024-RSA is 80-bits. Breaking RSA reduces to factoring RSA or ...


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In counter mode (CTR) no single block of cipher is dependent upon a previously calculated block. Each block can be calculated independently of every other block. This could be parallelized by splitting the cipher into chunks for individual threads to encrypt or decrypt. Say you have a 512 byte block of data you want to encrypt. Using AES128-CTR there ...


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It is depended to network structure and topology of your system, in some cases like distributed system you can use secret sharing scheme, such as shamir,rabin IDA or Krawcyk. Also you can use PKI for that. Usually in practice only hash of passwords are stored. But for key, shamir secret sharing scheme is powerful for storing key in secure way. That only an ...


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If I understood it well the end issue is to protect data from being recovered from deleted temp files. To address this problem use tools to shred the temp file and or folder instead of shift+delete. Deleting a files is nothing more than unlinking the address of the file from filesystem. Unless the contents of the location are over-written it is possible to ...


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How does work exactly the hybrid encryption RSA with AES? The long-term RSA keypair is used to exchange a temporary "session" key which is used to encrypt the traffic with AES. This can either be direct (i.e. generate key, encrypt with RSA public key, send to server, decrypt with RSA private key) or via a secondary key exchange mechanism (e.g. ...


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AES is a block cipher, meaning that the core operation processes only a block (of exactly 16 bytes with AES). When you want to "encrypt a file", you need to decide on how you split and shuffle your data, and what you actually send to the AES engine; this is called a mode of operation. All modes of operations are not equal. Moreover, some modes also offer ...


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According to NIST, The AES algorithm is capable of using cryptographic keys of 128, 192, and 256 bits to encrypt and decrypt data in block sizes of 128 bits (16 bytes). it means each block that goes as an input to the AES algorithm will be 16 bytes, so if your BUF_SIZE is 16 KB, when it wants to go to the AES, again it will be split to a blocks with 16 bytes ...


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In fact although you might be said to be performing the hash for lookup performance, it is being done to be PCI compliant. There are two ways of looking at this. Do x, it is the right thing to do. Do x, or we'll get caught not doing it. Doing x to prevent cracking does not really come into it, since there are only about 5 numbers to guess in some cases. ...


2

First, about AES-256 in particular: AES-256 is a symmetric cryptosystem. Decryption and encryption use the same key; if you encrypt stuff with a master key, you have to give that master key to whatever's decrypting stuff or else it can't decrypt stuff. You may have read about master and session keys, but that is about stuff happening before AES encryption -- ...


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I'll answer in order: almost certainly yes, asymmetric signatures in general take more space than the symmetric counterparts - RSA requires a certain amount of padding and a minimum key size to be secure; if you use a HMAC the minimum requirements for a secure HMAC - a hash based Message Authentication Code or keyed hash - would be about 64 bits / 8 bytes ...


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Asymmetric keys are only really valuable if one of them needs to be made public (though "public" can mean different things in different contexts). If you both generate and verify codes in private, than you can just use a private secret as part of an HMAC with a reasonable hashing algorithm. If space is a premium, you can even get away with using the ...


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Using symmetric or asymmetric encryption in this case really depends on the use case and not on the security aspects. How is the code generated? can the code requester have a common secret between himself and the code generator? If they do you can use HMAC to verify the sender and the integrity. If not, you can use asymmetric encryption to utilize signing of ...


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Can the serial be derived from the key? My recommendation is to use a 128 bit secret and use truncated HMAC("serial", secret) to derive the serial and HMAC("encryption", secret) to encrypt. If you have predetermined serials you must use and only have 128 bits to work with, I agree that using those 112 bits left is still safe. But you should still avoid ...


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There are no known attacks on AES that let an attacker turn partial knowledge of the key into full knowledge. If 16 bits of the key are easy to figure out, then you've got what is effectively a 112-bit key.



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