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budget:pysf [2012/10/06 19:55]
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budget:pysf [2012/10/06 20:45]
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 Since the size of the salts is variable, the checksum may occur later. Since the size of the salts is variable, the checksum may occur later.
  
-  * **Version:​** +  * **Version:​** ​version of file format, where least significant byte is a minor version indicating backward compatibility and most significant byte is a major version indicating incompatible format changes. 
-  * **Header length:** +  * **Header length:​** ​offset of file data from start of file, which may extend beyond the actual header (for example, to align with blocks on disk). 
-  * **Cipher:​** +  * **Cipher:​** ​identifies cipher algorithm used (e.g. AES). 
-  * **Mode:** +  * **Mode:​** ​indicates chaining mode (e.g. CBC). 
-  * **Key size:** +  * **Key size:​** ​size of key for encryption and checksum //in bytes// (e.g. 16 for 128-bit key). 
-  * **Salt size:** +  * **Salt size:​** ​size of salt used //in bytes// --- this determines the size of the two salt fields later and should be a multiple of 4 bytes to maintain alignment. 
-  * **Block size:** +  * **Block size:​** ​size of blocks into which file data is split prior to encryption, in bytes. 
-  * **Salt (encryption):​** +  * **Salt (encryption):​** ​salt used for generating encryption key from passphrase. 
-  * **Salt (checksum):​** +  * **Salt (checksum):​** ​salt used for generating key for HMAC checksumming from passphrase. 
-  * **Checksum:​**+  * **Checksum:​** ​the XOR of the HMAC-SHA1 sums of each //​encrypted//​ block of the file.
  
  
budget/pysf.txt · Last modified: 2012/10/12 07:32 (external edit)