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The "State" could not be re-used in OTP-22.0 or later.<br>
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/Hans Nilsson<br>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>Från:</b> erlang-questions-bounces@erlang.org <erlang-questions-bounces@erlang.org> för Zhengji Li <foldl@outlook.com><br>
<b>Skickat:</b> den 12 oktober 2019 12:15<br>
<b>Till:</b> Lista de Erlang <erlang-questions@erlang.org><br>
<b>Ämne:</b> [erlang-questions] crypto stream_state() used to be "self-contained" before OTP 22.0</font>
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<span>Hi all,</span></div>
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<span><br>
</span></div>
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Could we infer that "State" is a "self-contained" piece of raw data that we can pass </div>
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to different function calls?</div>
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<span style="color:rgb(0,0,0); font-family:calibri,helvetica,sans-serif; font-size:12pt; background-color:transparent"><span>stream_encrypt(State, PlainText) -> {NewState, CipherText}</span></span></div>
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<span style="color:rgb(0,0,0); font-family:calibri,helvetica,sans-serif; font-size:12pt; background-color:transparent"><span><br>
</span></span></div>
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<span style="color:rgb(0,0,0); font-family:calibri,helvetica,sans-serif; font-size:12pt; background-color:transparent">
<div>Compare it with:</div>
<div>file:<span>write(IoDevice, Bytes) -> ok | {error, Reason}</span><span><br>
</span></div>
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</span></div>
<div><span>I think the answer should be "Yes". And things truly works before OTP 22.0.</span></div>
<div><span><br>
</span></div>
<div>Although codes can be fixed for OTP 22 easily, my concern is that, if a function in OTP is declared as</div>
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</div>
<div>f(State, ...) -> {NewState, ...}</div>
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<div>Can we infer that the old State can be used again?</div>
<div><span><br>
</span></div>
<div><span>Below is a simple test.</span></div>
<div><span><br>
</span><span></span></div>
<div>```</div>
<div><span>t() -><br>
</span>
<div> Key = <<12,137,124,112,128,97,39,1,112,248,35,27,186,168,219,244>>,</div>
<div> IVec = <<78,237,251,180,107,173,97,170,32,214,233,193,147,64,117, 126>>,</div>
<div> Data = <<1,2,3,4>>,</div>
<div> Enc0 = enc(Key, IVec, Data),</div>
<div> Dec0 = dec(Key, IVec, Enc0),</div>
<div> show({Data, Enc0, Dec0}),</div>
<div></div>
<div> Cipher = crypto:stream_init(aes_ctr, Key, IVec),</div>
<div> Enc1 = enc(Cipher, Data),</div>
<div> Dec1 = dec(Cipher, Enc1),</div>
<div> show({Data, Enc1, Dec1}). % FAIL in OTP 22.0</div>
<div></div>
<div>enc(Key, IVec, Data) -></div>
<div> Cipher = crypto:stream_init(aes_ctr, Key, IVec),</div>
<div> {_, Enc} = crypto:stream_encrypt(Cipher, Data),</div>
<div> Enc.</div>
<div></div>
<div>dec(Key, IVec, Data) -></div>
<div> Cipher = crypto:stream_init(aes_ctr, Key, IVec),</div>
<div> {_, Dec} = crypto:stream_decrypt(Cipher, Data),</div>
<div> Dec.</div>
<div></div>
<div>enc(Cipher, Data) -></div>
<div> {_, Enc} = crypto:stream_encrypt(Cipher, Data),</div>
<div> Enc.</div>
<div></div>
<div>dec(Cipher, Data) -></div>
<div> {_, Dec} = crypto:stream_decrypt(Cipher, Data),</div>
<div> Dec.</div>
<div></div>
<div>show({A, B, A}) -> io:format("GOOD: ~p -> ~p -> ~p~n", [A,B,A]);</div>
<span>show({A, B, C}) -> io:format(" BAD: ~p -> ~p -> ~p~n", [A,B,C]).</span></div>
<div>```</div>
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