Is deriving a key in a context equivalent to RFC2898 PBKDF2?

[Miller, Timothy J.]

I.e., if I did:

data = <some data encrypted under a PBKDF2 derived key>
ctx = cryptCreateContext(CRYPT_UNUSED, CRYPT_ALGO_3DES);
s = cryptSetAttribute(ctx, CRYPT_CTXINFO_IV, iv, sizeof(iv));
s = cryptSetAttribute(ctx, CRYPT_CTXINFO_KEYING_ITERATIONS, count);
s = cryptSetAttributeString(ctx, CRYPT_CTXINFO_KEYING_SALT, salt,
sizeof(salt));
s = cryptSetAttributeString(ctx, CRYPT_CTXINFO_KEYING_VALUE, password,
sizeof(password));
s = cryptDecrypt(ctx, data, sizeof(data));

Do I get the right plaintext?  :)

-- Tim



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[Peter Gutmann]

"Timothy J. Miller" <tmiller@...> writes:

>I.e., if I did:
>
>data = <some data encrypted under a PBKDF2 derived key>
>ctx = cryptCreateContext(CRYPT_UNUSED, CRYPT_ALGO_3DES);
>s = cryptSetAttribute(ctx, CRYPT_CTXINFO_IV, iv, sizeof(iv));
>s = cryptSetAttribute(ctx, CRYPT_CTXINFO_KEYING_ITERATIONS, count);
>s = cryptSetAttributeString(ctx, CRYPT_CTXINFO_KEYING_SALT, salt, sizeof(salt));
>s = cryptSetAttributeString(ctx, CRYPT_CTXINFO_KEYING_VALUE, password, sizeof(password));
>s = cryptDecrypt(ctx, data, sizeof(data));
>
>Do I get the right plaintext?  :)

Yes, provided the values you're setting are the same as what was set when the
data was encrypted, that should give you the correct plaintext.

(Note that there's an easier way to do this, just use password-based
enveloping and the only thing you need to worry about is the password/key).

Peter.

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