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/*
* HKDF
* (C) 2013,2015 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/kdf_utils.h>
#include <botan/hkdf.h>
namespace Botan {
BOTAN_REGISTER_NAMED_T(KDF, "HKDF", HKDF, HKDF::make);
HKDF* HKDF::make(const Spec& spec)
{
if(auto mac = make_a<MessageAuthenticationCode>(spec.arg(0)))
return new HKDF(mac);
if(auto mac = make_a<MessageAuthenticationCode>("HMAC(" + spec.arg(0) + ")"))
return new HKDF(mac);
return nullptr;
}
size_t HKDF::kdf(byte out[], size_t out_len,
const byte secret[], size_t secret_len,
const byte salt[], size_t salt_len) const
{
m_prf->set_key(secret, secret_len);
byte counter = 1;
secure_vector<byte> h;
size_t offset = 0;
while(offset != out_len && counter != 0)
{
m_prf->update(h);
m_prf->update(salt, salt_len);
m_prf->update(counter++);
m_prf->final(h);
const size_t written = std::min(h.size(), out_len - offset);
copy_mem(&out[offset], &h[0], written);
offset += written;
}
return offset;
}
}
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