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/*************************************************
* EMSA3 Source File *
* (C) 1999-2007 Jack Lloyd *
*************************************************/
#include <botan/emsa3.h>
#include <botan/hash_id.h>
#include <botan/lookup.h>
namespace Botan {
namespace {
/*************************************************
* EMSA3 Encode Operation *
*************************************************/
SecureVector<byte> emsa3_encoding(const MemoryRegion<byte>& msg,
u32bit output_bits,
const MemoryRegion<byte>& hash_id,
u32bit hash_size)
{
if(msg.size() != hash_size)
throw Encoding_Error("EMSA3::encoding_of: Bad input length");
u32bit output_length = output_bits / 8;
if(output_length < hash_id.size() + hash_size + 10)
throw Encoding_Error("EMSA3::pad: Output length is too small");
SecureVector<byte> T(output_length);
const u32bit P_LENGTH = output_length - hash_size - hash_id.size() - 2;
T[0] = 0x01;
set_mem(T+1, P_LENGTH, 0xFF);
T[P_LENGTH+1] = 0x00;
T.copy(P_LENGTH+2, hash_id, hash_id.size());
T.copy(output_length-hash_size, msg, msg.size());
return T;
}
}
/*************************************************
* EMSA3 Update Operation *
*************************************************/
void EMSA3::update(const byte input[], u32bit length)
{
hash->update(input, length);
}
/*************************************************
* Return the raw (unencoded) data *
*************************************************/
SecureVector<byte> EMSA3::raw_data()
{
return hash->final();
}
/*************************************************
* EMSA3 Encode Operation *
*************************************************/
SecureVector<byte> EMSA3::encoding_of(const MemoryRegion<byte>& msg,
u32bit output_bits,
RandomNumberGenerator&)
{
return emsa3_encoding(msg, output_bits, hash_id,
hash->OUTPUT_LENGTH);
}
/*************************************************
* Default signature decoding *
*************************************************/
bool EMSA3::verify(const MemoryRegion<byte>& coded,
const MemoryRegion<byte>& raw,
u32bit key_bits) throw()
{
try
{
return (coded == emsa3_encoding(raw, key_bits,
hash_id,
hash->OUTPUT_LENGTH));
}
catch(...)
{
return false;
}
}
/*************************************************
* EMSA3 Constructor *
*************************************************/
EMSA3::EMSA3(const std::string& hash_name)
{
hash = get_hash(hash_name);
hash_id = pkcs_hash_id(hash->name());
}
}
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