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/*************************************************
* PKCS1 EME Source File *
* (C) 1999-2007 Jack Lloyd *
*************************************************/
#include <botan/eme.h>
namespace Botan {
/*************************************************
* PKCS1 Pad Operation *
*************************************************/
SecureVector<byte> EME_PKCS1v15::pad(const byte in[], u32bit inlen,
u32bit olen,
RandomNumberGenerator& rng) const
{
olen /= 8;
if(olen < 10)
throw Encoding_Error("PKCS1: Output space too small");
if(inlen > olen - 10)
throw Encoding_Error("PKCS1: Input is too large");
SecureVector<byte> out(olen);
out[0] = 0x02;
for(u32bit j = 1; j != olen - inlen - 1; ++j)
while(out[j] == 0)
out[j] = rng.next_byte();
out.copy(olen - inlen, in, inlen);
return out;
}
/*************************************************
* PKCS1 Unpad Operation *
*************************************************/
SecureVector<byte> EME_PKCS1v15::unpad(const byte in[], u32bit inlen,
u32bit key_len) const
{
if(inlen != key_len / 8 || inlen < 10 || in[0] != 0x02)
throw Decoding_Error("PKCS1::unpad");
u32bit seperator = 0;
for(u32bit j = 0; j != inlen; ++j)
if(in[j] == 0)
{
seperator = j;
break;
}
if(seperator < 9)
throw Decoding_Error("PKCS1::unpad");
return SecureVector<byte>(in + seperator + 1, inlen - seperator - 1);
}
/*************************************************
* Return the max input size for a given key size *
*************************************************/
u32bit EME_PKCS1v15::maximum_input_size(u32bit keybits) const
{
if(keybits / 8 > 10)
return ((keybits / 8) - 10);
else
return 0;
}
}
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