Re: 2 Keys decrypts same message

From: 小葉南洋杉 (john65537_at_yahoo.com.tw)
Date: 07/08/03 

Date: 7 Jul 2003 20:47:55 -0700

Another idea for this interesting question.

Let each user's row D be encrypted by the hash of his/her password H(P),
call the cipher as C1,
also encrypt H(P) with the master key K_m, call this cipher as C2.

Thus, DB stores two ciphers, C1 and C2.

Most of the time, a user provides correct password P, and decrypt
C1 with the key H(P) to retrieve D.

When a user forgets P, K_m can be used to decrypt C2
and get the encryption key H(P) to decrypt & retrieve D.

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