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master research student in ubiquitous-IT currently focusing on consumer cloud storage


Jun
25
comment Is a PBKDF2-derived master key easier cracked if very many Data Protection Keys are derived from it?
@IlmariKaronen thanks for the clear and throughout explanation!
Jun
25
comment Is a PBKDF2-derived master key easier cracked if very many Data Protection Keys are derived from it?
Ya pretty complete answer. But I have a question about the 2nd part (salt) If I use random salt for each DPK for each file, I need to store it somewhere right? Either append infront of encrypted file, or maybe store in a database. But if I use Salt = Label+Context, it would be easier as I can retrieve it easily and I don't need to store it somewhere.
May
5
comment Encrypt a single file, chunk-by-chunk, each chunk using different key (AES)
@PaĆ­loEbermann for improved bandwidth utilization, bypassing limited upload size, and some minor security improvement. Yes, if any of them fails, data cannot be reconstructed. But I added erasure coding(RAID5) instead of simple data striping(RAID0), so it protects from several providers fails, depending on my scheme (3+1) (4+2) etc
May
2
comment Encrypt a single file, chunk-by-chunk, each chunk using different key (AES)
Thanks for all the suggestions, they are very helpful. I will redesign my scheme following your suggestions. It is an unpublished Android application, that is planned for published in google market on a later date, as an free app. So, I think it is not misleading =) Anyway, to be honest, it is not really a school project, it is for my master thesis and a journal (writing now, submitting soon).
May
2
comment Encrypt a single file, chunk-by-chunk, each chunk using different key (AES)
oops, forgot to mention that another reason for using pipeline is because each chunk is go through several steps like splitting, erasure-coding, compression, encryption and finally checksum. That's why I will need to process the file chunk-by-chunk in parallel, else it will take a long time. To be honest, the multi-keys encryption is just some add-on to make my school project looks bigger =) If it is really flawed, I will scrap this part out of the project. Needing your further advice.
May
2
comment Encrypt a single file, chunk-by-chunk, each chunk using different key (AES)
My idea was, an attacker needs to know many things before he can decrypt my file 1) password for each cloud storage 2) password for file encryption 3) password for database It also protects from bad provider who look at your data For integrity check, I do provide CRC32 or SHA1-256 checksum based on user preference
May
2
comment Encrypt a single file, chunk-by-chunk, each chunk using different key (AES)
Thanks for the reply! 1) I want to achieve something like a two-pass encryption, thats why I am asking 2 passwords from user. 2) I split the file into chunks, because I am uploading each chunk to different cloud storage (which can benefits from improved bandwidth utilization, and a little bit of security thru obscurity) 3) Another reason for split file is because I am encrypting each chunk in a pipeline method (first 4 chunks are encrypted in parallel), it is faster than encrypt the whole file at once. different key for each chunk is just some add-on, since I have to split file no matter how.