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/*
* HKDF
* (C) 2013,2015 Jack Lloyd
* (C) 2016 René Korthaus, Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/hkdf.h>
namespace Botan {
size_t HKDF::kdf(byte key[], size_t key_len,
const byte secret[], size_t secret_len,
const byte salt[], size_t salt_len,
const byte label[], size_t label_len) const
{
HKDF_Extract extract(m_prf->clone());
HKDF_Expand expand(m_prf->clone());
secure_vector<byte> prk(m_prf->output_length());
extract.kdf(prk.data(), prk.size(), secret, secret_len, salt, salt_len, nullptr, 0);
return expand.kdf(key, key_len, prk.data(), prk.size(), nullptr, 0, label, label_len);
}
size_t HKDF_Extract::kdf(byte key[], size_t key_len,
const byte secret[], size_t secret_len,
const byte salt[], size_t salt_len,
const byte[], size_t) const
{
secure_vector<byte> prk;
if(salt_len == 0)
{
m_prf->set_key(std::vector<byte>(m_prf->output_length()));
}
else
{
m_prf->set_key(salt, salt_len);
}
m_prf->update(secret, secret_len);
m_prf->final(prk);
const size_t written = std::min(prk.size(), key_len);
copy_mem(&key[0], prk.data(), written);
return written;
}
size_t HKDF_Expand::kdf(byte key[], size_t key_len,
const byte secret[], size_t secret_len,
const byte salt[], size_t salt_len,
const byte label[], size_t label_len) const
{
m_prf->set_key(secret, secret_len);
byte counter = 1;
secure_vector<byte> h;
size_t offset = 0;
while(offset != key_len && counter != 0)
{
m_prf->update(h);
m_prf->update(label, label_len);
m_prf->update(salt, salt_len);
m_prf->update(counter++);
m_prf->final(h);
const size_t written = std::min(h.size(), key_len - offset);
copy_mem(&key[offset], h.data(), written);
offset += written;
}
return offset;
}
}
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