module Keystores

This is an implementation of a Sun proprietary, exportable algorithm intended for use when protecting (or recovering the cleartext version of) sensitive keys. This algorithm is not intended as a general purpose cipher.

This is how the algorithm works for key protection: p - user password s - random salt X - xor key P - to-be-protected key Y - protected key R - what gets stored in the keystore

Step 1: Take the user's password, append a random salt (of fixed size) to it, and hash it: d1 = digest(p, s) Store d1 in X.

Step 2: Take the user's password, append the digest result from the previous step, and hash it: dn = digest(p, dn-1). Store dn in X (append it to the previously stored digests). Repeat this step until the length of X matches the length of the private key P.

Step 3: XOR X and P, and store the result in Y: Y = X XOR P.

Step 4: Store s, Y, and digest(p, P) in the result buffer R: R = s + Y + digest(p, P), where “+” denotes concatenation. (NOTE: digest(p, P) is stored in the result buffer, so that when the key is recovered, we can check if the recovered key indeed matches the original key.) R is stored in the keystore.

The protected key is recovered as follows:

Step1 and Step2 are the same as above, except that the salt is not randomly generated, but taken from the result R of step 4 (the first length(s) bytes).

Step 3 (XOR operation) yields the plaintext key.

Then concatenate the password with the recovered key, and compare with the last length(digest(p, P)) bytes of R. If they match, the recovered key is indeed the same key as the original key.

TODO, implement this as an OpenSSL PBE Cipher