What do I wrong? Botan & QT & SHELL decrypting - c++

Question

first i create my singing keys:
(Shell/Debian 9)
>openssl genrsa -out ./priv.rsa 2048
>openssl pkcs8 -topk8 -inform PEM -outform PEM -in ./priv.rsa -out priv.pem
>openssl rsa -in ./priv.pem -pubout -out pub.pem
Then i ceate my encrypt.txt with
(Shell)
> echo "ęśłżół">encrypt.txt
and crypt it with my public Rsa key
(Shell)
> openssl rsautl -encrypt -inkey ./pub.pem -pubin -in ./encrypt.txt -out
> ./encrypt.dat
.. and than comes Botan (dowloaded yesterday) with QT (5.9.1):
...
using namespace Botan;
using std::string;
QFile file,file2;
// Reading private key
file.setFileName(".../priv.pem");
file.open(QIODevice::ReadOnly);
QByteArray f = file.readAll();
file.close();
//reading encrypted file
file2.setFileName("...../encrypt.dat");
file2.open(QIODevice::ReadOnly);
QByteArray f2 = file2.readAll();
file2.close();
enter code here
std::vector<uint8_t> ct;
for(QByteArray::Iterator it = f2.begin();it!=f2.end();it++)
{
ct.push_back((uint8_t)(*it));
}
string password=ui->lineEdit_2->text().toStdString().c_str();
std::unique_ptr<Botan::RandomNumberGenerator> rng(new Botan::AutoSeeded_RNG);
DataSource_Memory keyData2( f.toStdString().c_str() );
std::unique_ptr<Private_Key> kp = PKCS8::load_key(keyData2,pass);
PK_Decryptor_EME dec(*kp,*rng.get(), "Raw");
secure_vector<uint8_t> ct4=dec.decrypt(ct);
QByteArray aaa;
for(secure_vector<uint8_t>::iterator it=ct4.begin();it!=ct4.end();it++)
{
aaa+=(uint8_t)(*it);
}
QFile fileX(".../encryptE.txt");
fileX.open(QIODevice::WriteOnly);
fileX.write(aaa);
fileX.close();
...and my Out file contains (and is 255 byte wide):
^B4�����x��^V�&��ߵݹ�*S�^T�㓠K��7�J CF^U^B^[��^Q��
=^H�+�7Y^^^U�^^O\�v�����bdK^N^Ev^QI=����)�)��n^KПV����Y�-23^^�5]���^\�լ1^U�9n�z萘Å^A��Vr��8�#^C�^S����o��0����S[x�
��2 �^P4�^L�p��i���t^D���
��^Z��J^K�^G^Z^\�4\^D^Z^Ew^Tx�S�ٛ��i�5�^D��A��Ƨ�o�zÚ��#���^L�^G���Ŋ^FXIu��^#ęśłżół
My questions:
1. ... i see my string: ęśłżół .... but what do I wrong ? - decodedfile isn't orginal one?
I'is allowed to my to use RAW type only like (FOR THIS FILE: encrpted.dat):
PK_Decryptor_EME dec(*kp,*rng.get(), "Raw");
if i choose : PKCS1v15” || “EME-PKCS1-v1_5”
“OAEP” || “EME-OAEP” || “EME1” || “EME1(SHA-1)” || “EME1(SHA-256)”
i become error:
terminate called after throwing an instance of 'Botan::Decoding_Error'
what(): Invalid argument Decoding error: Invalid public key ciphertext, cannot decrypt

Answer 1

OpenSSL defaults to the less secure PKCS#1 v1.5 padding. To use the same unpadding you should probably use "PKCS1v15" in Botan.
Beware that PKCS#1 v1.5 is succeptible to the Bleichenbacher (padding oracle) attack, so the use of PKCS#1 v1.5 padding should be used with care (i.e. not in automated systems that can act as a padding oracle).
Using OAEP is recommended.