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diff --git a/lib/crypto/doc/src/new_api.xml b/lib/crypto/doc/src/new_api.xml new file mode 100644 index 0000000000..66eeefb692 --- /dev/null +++ b/lib/crypto/doc/src/new_api.xml @@ -0,0 +1,209 @@ +<?xml version="1.0" encoding="utf-8" ?> +<!DOCTYPE chapter SYSTEM "chapter.dtd"> + +<chapter> + <header> + <copyright> + <year>2014</year><year>2019</year> + <holder>Ericsson AB. All Rights Reserved.</holder> + </copyright> + <legalnotice> + The contents of this file are subject to the Erlang Public License, + Version 1.1, (the "License"); you may not use this file except in + compliance with the License. You should have received a copy of the + Erlang Public License along with this software. If not, it can be + retrieved online at http://www.erlang.org/. + + Software distributed under the License is distributed on an "AS IS" + basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See + the License for the specific language governing rights and limitations + under the License. + + </legalnotice> + + <title>New and Old API</title> + <prepared>Hans Nilsson</prepared> + <docno></docno> + <date>2019-08-22</date> + <rev>A</rev> + <file>new_api.xml</file> + </header> + <p> + This chapter describes the new api to encryption and decryption. + </p> + + <section> + <title>Background</title> + <p>The CRYPTO app has evolved during its lifetime. Since also the OpenSSL cryptolib has changed the + API several times, there are parts of the CRYPTO app that uses a very old one internally and + other parts that uses the latest one. The internal definitions of e.g cipher names was a bit hard + to maintain. + </p> + <p>It turned out that using the old api in the new way (more about that later), and still keep it + backwards compatible was not possible. Specially as more precision in the error messages was wanted + it could not be combined with the old standard. + </p> + <p>Therefore the old api (see next section) is kept for now but internally implemented with new primitives. + </p> + </section> + + <section> + <title>The old API</title> + <p>The old functions - not recommended for new programs - are:</p> + <list> + <item><seealso marker="crypto#block_encrypt-3">block_encrypt/3</seealso></item> + <item><seealso marker="crypto#block_encrypt-4">block_encrypt/4</seealso></item> + <item><seealso marker="crypto#block_decrypt-3">block_decrypt/3</seealso></item> + <item><seealso marker="crypto#block_decrypt-4">block_decrypt/4</seealso></item> + <item><seealso marker="crypto#stream_init-2">stream_init/2</seealso></item> + <item><seealso marker="crypto#stream_init-2">stream_init/3</seealso></item> + <item><seealso marker="crypto#stream_encrypt-2">stream_encrypt/2</seealso></item> + <item><seealso marker="crypto#stream_decrypt-2">stream_decrypt/2</seealso></item> + </list> + <p>They are not deprecated for now, but may be in a future. + </p> + </section> + + <section> + <title>The new API</title> + <p>The new functions for encrypting or decrypting one single text in one binary are: + </p> + <list> + <item><seealso marker="crypto#crypto_one_time/4">crypto_one_time/4</seealso></item> + <item><seealso marker="crypto#crypto_one_time/5">crypto_one_time/5</seealso></item> + <item><seealso marker="crypto#crypto_aead/6">crypto_aead/6</seealso></item> + <item><seealso marker="crypto#crypto_aead/7">crypto_aead/7</seealso></item> + </list> + <p>The <c>crypto_aead</c> functions are for the ciphers of mode <c>ccm</c> or + <c>gcm</c>, and for the cipher <c>chacha20-poly1305</c>. + </p> + <p>For repeated encryption or decryption of a text divided in parts, where the parts are handled + one by one but in sequence, the functions are: + </p> + <list> + <item><seealso marker="crypto#crypto_init/4">crypto_init/4</seealso></item> + <item><seealso marker="crypto#crypto_init/3">crypto_init/3</seealso></item> + <item><seealso marker="crypto#crypto_update/2">crypto_update/2</seealso></item> + </list> + <p>The <c>crypto_init</c> initialies a cipher operation and one or more calls of + <c>crypto_update</c> does the acual encryption or decryption. Note that AEAD ciphers + can't be handled this way due to their nature. + </p> + <p>Finally, for repeated encryption or decryption of a text divided in parts where the + same cipher and same key is used, but a new initialization vector (nounce) should be applied + for each part, the functions are: + </p> + <list> + <item><seealso marker="crypto#crypto_init_dyn_iv/3">crypto_init_dyn_iv/3</seealso></item> + <item><seealso marker="crypto#crypto_update_dyn_iv/3">crypto_update_dyn_iv/3</seealso></item> + </list> + <p>An example of where those functions are needed, is when handling the TLS protocol.</p> + + <section> + <title>Examples of crypto_init/4 and crypto_update/2</title> + <p>Encrypting two blocks:</p> + <code type="erl"> + 1> crypto:start(). + ok + 2> Key = <<1:128>>, + 2> IV = <<0:128>>, + 2> StateEnc = crypto:crypto_init(aes_128_ctr, Key, IV, true). % encrypt -> true + #Ref<0.3768901617.1128660993.124047> + 3> crypto:crypto_update(StateEnc, <<"First bytes">>). + <<67,44,216,166,25,130,203,5,66,6,162>> + 4> crypto:crypto_update(StateEnc, <<"Second bytes">>). + <<16,79,94,115,234,197,94,253,16,144,151,41>> + 5> + 5> StateDec = crypto:crypto_init(aes_128_ctr, Key, IV, false). % decrypt -> false + #Ref<0.3768901617.1128660994.124255> + 6> crypto:crypto_update(StateDec, <<67,44,216,166,25,130,203>>). + <<"First b">> + 7> crypto:crypto_update(StateDec, <<5,66,6,162,16,79,94,115,234,197, + 94,253,16,144,151>>). + <<"ytesSecond byte">> + 8> crypto:crypto_update(StateDec, <<41>>). + <<"s">> + 9> + </code> + <p>Note that the data that the <c>StateEnc</c> and <c>StateDec</c> references are destructivly + updated by the calls to <seealso marker="crypto#crypto_update/2">crypto_update/2</seealso>. + This is to gain time in the calls of the nifs interfacing the cryptolib. In a loop where the + state is saved in the loop's state, it also saves one update of the loop state per crypto operation. + </p> + <p>For example, a simple server receiving text parts to encrypt and send the result back to the + one who sent them (the <c>Requester</c>): + </p> + <code type="erl"> + encode(Crypto, Key, IV) -> + crypto_loop(crypto:crypto_init(Crypto, Key, IV, true)). + + crypto_loop(State) -> + receive + {Text, Requester} -> + Requester ! crypto:crypto_update(State, Text), + loop(State) + end. + </code> + <p>Note that the <c>State</c> is not updated. Such updates could be costly if the loop state + is a tuple or record with many elements. + </p> + </section> + + <section> + <title>Example of crypto_one_time/5</title> + <p>The same eample as in the + <seealso marker="#examples-of-crypto_init-4-and-crypto_update-2">previous section</seealso>, + but now with one call to <c>crypto_one_time/5</c>: + </p> + <code> + 2> Key = <<1:128>>, + 2> IV = <<0:128>>, + 2> Txt = [<<"First bytes">>,<<"Second bytes">>], + 2> crypto:crypto_one_time(aes_128_ctr, Key, IV, Txt, true). + <<67,44,216,166,25,130,203,5,66,6,162,16,79,94,115,234, + 197,94,253,16,144,151,41>> + 3> + </code> + <p>The <c>[<<"First bytes">>,<<"Second bytes">>]</c> could of course have been one + single binary: <c><<"First bytesSecond bytes">></c>. + </p> + </section> + </section> + + <section> + <title>Retired cipher names</title> + <p>This table lists the retired cipher names in the first column and suggests names to replace them with + in the second column. + </p> + <p>The new names follows the OpenSSL libcrypto names. The format is ALGORITM_KEYSIZE_MODE. + </p> + <p>Examples of algorithms are aes, chacha20 and des. The keysize is the number of bits + and examples of the mode are cbc, ctr and gcm. The mode may be followed by a number depending + on the mode. An example is the ccm mode which has a variant called ccm8 where the so called tag + has a length of eight bits. + </p> + <p>The old names had by time lost any common naming which the new names now introduces. The new names include + the key length which improves the error checking in the lower levels of the crypto application. + </p> + + <table> + <row><cell><strong>Instead of:</strong></cell> <cell><strong>Use:</strong> </cell></row> + + <row><cell><c>aes_cbc128</c> </cell> <cell> <c>aes_128_cbc</c> </cell></row> + <row><cell><c>aes_cbc256</c> </cell> <cell> <c>aes_256_cbc</c> </cell></row> + <row><cell><c>aes_cbc</c> </cell> <cell> <c>aes_128_cbc, aes_192_cbc, aes_256_cbc</c></cell></row> + <row><cell><c>aes_ccm</c> </cell> <cell> <c>aes_128_ccm, aes_192_ccm, aes_256_ccm</c></cell></row> + <row><cell><c>aes_cfb128</c> </cell> <cell> <c>aes_128_cfb128, aes_192_cfb128, aes_256_cfb128</c></cell></row> + <row><cell><c>aes_cfb8</c> </cell> <cell> <c>aes_128_cfb8, aes_192_cfb8, aes_256_cfb8</c></cell></row> + <row><cell><c>aes_ctr</c> </cell> <cell> <c>aes_128_ctr, aes_192_ctr, aes_256_ctr</c></cell></row> + <row><cell><c>aes_gcm</c> </cell> <cell> <c>aes_128_gcm, aes_192_gcm, aes_256_gcm</c></cell></row> + <row><cell><c>des3_cbc</c> </cell> <cell> <c>des_ede3_cbc</c></cell></row> + <row><cell><c>des3_cbf</c> </cell> <cell> <c>des_ede3_cfb</c></cell></row> + <row><cell><c>des3_cfb</c> </cell> <cell> <c>des_ede3_cfb</c></cell></row> + <row><cell><c>des_ede3</c> </cell> <cell> <c>des_ede3_cbc</c></cell></row> + <row><cell><c>des_ede3_cbf</c> </cell> <cell> <c>des_ede3_cfb</c></cell></row> + <tcaption></tcaption> + </table> + </section> + +</chapter> |