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flesh out comment for generateHeaderPadding

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This commit is contained in:
Olaoluwa Osuntokun 2015-10-17 14:34:06 -07:00
parent 4efb397ade
commit 037b1f47ee
1 changed files with 10 additions and 9 deletions
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19
sphinx.go
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@ -179,15 +179,16 @@ func GenerateSphinxHeader(dest []byte, identifier [securityParameter]byte,
return header, hopSharedSecrets, nil
}
// generateHeaderPadding...
// At each step, we add 2*securityParameter padding of zeroes, concatenate it
// to the previous filler, then decrypt it (XOR) with the secret key of the
// current hop. When encrypting the mix header we essentially do the reverse of
// this operation: we "encrypt" the padding, and drop 2*k number of zeroes. As
// nodes process the mix header they add the padding (2*k) and then decrypt
// eventually leaving only the original "filler" bytes produced by this function
// at the last hop. Using this methodology, the size of the mix header stays
// constant at each hop.
// generateHeaderPadding derives the bytes for padding the mix header to ensure
// it remains fixed sized throughout route transit. At each step, we add
// 2*securityParameter padding of zeroes, concatenate it to the previous
// filler, then decrypt it (XOR) with the secret key of the current hop. When
// encrypting the mix header we essentially do the reverse of this operation:
// we "encrypt" the padding, and drop 2*k number of zeroes. As nodes process
// the mix header they add the padding (2*k) in order to check the MAC and
// decrypt the next routing information eventually leaving only the original
// "filler" bytes produced by this function at the last hop. Using this
// methodology, the size of the mix header stays constant at each hop.
func generateHeaderPadding(numHops int, sharedSecrets [][sharedSecretSize]byte) []byte {
var filler []byte
for i := 1; i < numHops; i++ {