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HMAC is generally more applicable to situations where two entities want to communicate securely over the internet. It provides two key things, confidentiality and integrity. confidentiality by proving the remote client has possession of the "secret" ingredient, integrity, through validation of message digest. In your use case, local storage encryption, ...


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Here are some weaknesses (the first one is the most serious): If you do not include the encryption IV in the input to HMAC, then attackers could modify the IV and induce a corresponding change in the message without being detected. Similarly, the attacker could modify SALT1 or ITERATIONS1; the HMAC would still match, but you would get junk upon decryption. ...


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If the server is going to decrypt the data when presented with the user's key, that second layer of encryption does not protect against a leaked user's key. Whoever has that key can decrypt the data. A second layer of encryption does make a brute force attack harder, but if the key for the second layer is stored with the data that advantage vanishes as ...


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I would recommend using an existing solution such as SQLCipher, which already works fine on Android and let you store all kinds of data in one database (or if you wish, several separate ones). This would certainly be easier and more secure than trying to implement your own file encryption.


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According to the comments, I would suggest doing simple AES on the server side. Eg, when a customer wants to open a document, he request decryption, and then the document are sent to server, decrypted and then sent back. The decrypted document are then never stored on flash or memory, only in RAM. Once the user are inactive a certain period or switches to a ...


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Before I give my answer, lets first go over the subject of HMAC. Hash-based message authentication code (or HMAC) is a mechanism for calculating a message authentication code involving a hash function in combination with a secret key. This can be used to verify the integrity and authenticity of a a message. Now HMAC authentication guarantees the ...


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The AES competition received 15 candidates, two of which suffered from "academic breaks" (weaknesses that are only theoretical, but still demonstrate that the underlying block cipher is not "optimally secure"). The remaining 13 are, to my knowledge, still unbroken to this day. Therefore, the choice of Rijndael had to be done for reasons other than security. ...


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On software encryption vs hardware encryption, read this comparison on Kingston's website, and your choice may be easy, but this is marketing language. I'm quite sure that Open Source software encryption like GPG is more secure. See this question: Is hardware based disk encryption more secure that software based?. The basic question is: from who do you ...


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That's right, if the attacker modify one or multiple bits of data that encrypted with AES algorithm, it's not possible to decrypt the data on client .


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My understanding of NFC is that, as a standard, it doesn't offer any provision for encryption of data security. This means you'll have to implement security on top of it. So first: the important part: do not try to implement it yourself: You do not have the understanding necessary to design it properly (as demonstrated by your question) Even with proper ...


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At least the block where the attacker does the modification, its information will not be recoverable (you'll recover senseless info, be careful on that also because it may have sense even!), but depending on the block cipher mode it could disturb your decryption in a longer set. No information is released on that, but how you react to this issue may release ...



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