1EVP_KDF_TLS1_PRF(7)                 OpenSSL                EVP_KDF_TLS1_PRF(7)
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NAME

6       EVP_KDF_TLS1_PRF - The TLS1 PRF EVP_KDF implementation
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DESCRIPTION

9       Support for computing the TLS1 PRF through the EVP_KDF API.
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11       The EVP_KDF_TLS1_PRF algorithm implements the PRF used by TLS versions
12       up to and including TLS 1.2.
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14   Numeric identity
15       EVP_KDF_TLS1_PRF is the numeric identity for this implementation; it
16       can be used with the EVP_KDF_CTX_new_id() function.
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18   Supported controls
19       The supported controls are:
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21       EVP_KDF_CTRL_SET_MD
22           This control works as described in "CONTROLS" in EVP_KDF_CTX(3).
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24           The "EVP_KDF_CTRL_SET_MD" control is used to set the message digest
25           associated with the TLS PRF.  EVP_md5_sha1() is treated as a
26           special case which uses the PRF algorithm using both MD5 and SHA1
27           as used in TLS 1.0 and 1.1.
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29       EVP_KDF_CTRL_SET_TLS_SECRET
30           This control expects two arguments: "unsigned char *sec", "size_t
31           seclen"
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33           Sets the secret value of the TLS PRF to seclen bytes of the buffer
34           sec.  Any existing secret value is replaced.
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36           EVP_KDF_ctrl_str() takes two type strings for this control:
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38           "secret"
39               The value string is used as is.
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41           "hexsecret"
42               The value string is expected to be a hexadecimal number, which
43               will be decoded before being passed on as the control value.
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45       EVP_KDF_CTRL_RESET_TLS_SEED
46           This control does not expect any arguments.
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48           Resets the context seed buffer to zero length.
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50       EVP_KDF_CTRL_ADD_TLS_SEED
51           This control expects two arguments: "unsigned char *seed", "size_t
52           seedlen"
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54           Sets the seed to seedlen bytes of seed.  If a seed is already set
55           it is appended to the existing value.
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57           The total length of the context seed buffer cannot exceed 1024
58           bytes; this should be more than enough for any normal use of the
59           TLS PRF.
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61           EVP_KDF_ctrl_str() takes two type strings for this control:
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63           "seed"
64               The value string is used as is.
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66           "hexseed"
67               The value string is expected to be a hexadecimal number, which
68               will be decoded before being passed on as the control value.
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NOTES

71       A context for the TLS PRF can be obtained by calling:
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73        EVP_KDF_CTX *kctx = EVP_KDF_CTX_new_id(EVP_KDF_TLS1_PRF, NULL);
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75       The digest, secret value and seed must be set before a key is derived
76       otherwise an error will occur.
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78       The output length of the PRF is specified by the "keylen" parameter to
79       the EVP_KDF_derive() function.
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EXAMPLE

82       This example derives 10 bytes using SHA-256 with the secret key
83       "secret" and seed value "seed":
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85        EVP_KDF_CTX *kctx;
86        unsigned char out[10];
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88        kctx = EVP_KDF_CTX_new_id(EVP_KDF_TLS1_PRF);
89        if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_MD, EVP_sha256()) <= 0) {
90            error("EVP_KDF_CTRL_SET_MD");
91        }
92        if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_TLS_SECRET,
93                         "secret", (size_t)6) <= 0) {
94            error("EVP_KDF_CTRL_SET_TLS_SECRET");
95        }
96        if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_ADD_TLS_SEED, "seed", (size_t)4) <= 0) {
97            error("EVP_KDF_CTRL_ADD_TLS_SEED");
98        }
99        if (EVP_KDF_derive(kctx, out, sizeof(out)) <= 0) {
100            error("EVP_KDF_derive");
101        }
102        EVP_KDF_CTX_free(kctx);
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SEE ALSO

105       EVP_KDF_CTX, EVP_KDF_CTX_new_id(3), EVP_KDF_CTX_free(3),
106       EVP_KDF_ctrl(3), EVP_KDF_derive(3), "CONTROLS" in EVP_KDF_CTX(3)
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109       Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.
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111       Licensed under the Apache License 2.0 (the "License").  You may not use
112       this file except in compliance with the License.  You can obtain a copy
113       in the file LICENSE in the source distribution or at
114       <https://www.openssl.org/source/license.html>.
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1181.1.1c                            2019-06-03               EVP_KDF_TLS1_PRF(7)
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