| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | EVP_chacha20,
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| 6 | EVP_chacha20_poly1305
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| 7 | - EVP ChaCha20 stream cipher
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| 8 |
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| 9 | =head1 SYNOPSIS
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| 10 |
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| 11 | #include <openssl/evp.h>
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| 12 |
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| 13 | const EVP_CIPHER *EVP_chacha20(void);
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| 14 | const EVP_CIPHER *EVP_chacha20_poly1305(void);
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| 15 |
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| 16 | =head1 DESCRIPTION
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| 17 |
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| 18 | The ChaCha20 stream cipher for EVP.
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| 19 |
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| 20 | =over 4
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| 21 |
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| 22 | =item EVP_chacha20()
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| 23 |
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| 24 | The ChaCha20 stream cipher. The key length is 256 bits, the IV is 128 bits long.
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| 25 | The first 64 bits consists of a counter in little-endian order followed by a 64
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| 26 | bit nonce. For example a nonce of:
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| 27 |
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| 28 | 0000000000000002
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| 29 |
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| 30 | With an initial counter of 42 (2a in hex) would be expressed as:
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| 31 |
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| 32 | 2a000000000000000000000000000002
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| 33 |
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| 34 | =item EVP_chacha20_poly1305()
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| 35 |
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| 36 | Authenticated encryption with ChaCha20-Poly1305. Like EVP_chacha20(), the key
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| 37 | is 256 bits and the IV is 96 bits. This supports additional authenticated data
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| 38 | (AAD) and produces a 128-bit authentication tag. See the
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| 39 | L<EVP_EncryptInit(3)/AEAD Interface> section for more information.
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| 40 |
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| 41 | =back
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| 42 |
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| 43 | =head1 NOTES
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| 44 |
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| 45 | Developers should be aware of the negative performance implications of
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| 46 | calling these functions multiple times and should consider using
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| 47 | L<EVP_CIPHER_fetch(3)> with L<EVP_CIPHER-CHACHA(7)> instead.
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| 48 | See L<crypto(7)/Performance> for further information.
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| 49 |
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| 50 | L<RFC 7539|https://www.rfc-editor.org/rfc/rfc7539.html#section-2.4>
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| 51 | uses a 32 bit counter and a 96 bit nonce for the IV.
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| 52 |
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| 53 | =head1 RETURN VALUES
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| 54 |
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| 55 | These functions return an B<EVP_CIPHER> structure that contains the
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| 56 | implementation of the symmetric cipher. See L<EVP_CIPHER_meth_new(3)> for
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| 57 | details of the B<EVP_CIPHER> structure.
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| 58 |
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| 59 | =head1 SEE ALSO
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| 60 |
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| 61 | L<evp(7)>,
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| 62 | L<EVP_EncryptInit(3)>,
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| 63 | L<EVP_CIPHER_meth_new(3)>
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| 64 |
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| 65 | =head1 COPYRIGHT
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| 66 |
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| 67 | Copyright 2017-2023 The OpenSSL Project Authors. All Rights Reserved.
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| 68 |
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| 69 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 70 | this file except in compliance with the License. You can obtain a copy
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| 71 | in the file LICENSE in the source distribution or at
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| 72 | L<https://www.openssl.org/source/license.html>.
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| 73 |
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| 74 | =cut
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| 75 |
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