Edit: To bear clear, the encrypted buffer was encrypted with the private key. I am trying to decrypt, with the public key, data that was encrypted with the private key.

I’m trying to perform RSA decryption with a public key using the BCrypt API, but BCryptDecrypt always returns STATUS_INVALID_PARAMETER. Does BCrypt not allow decrypt with a public key?

Some error checking and resource cleanup removed for brevity. BCryptDecrypt is where I receive a failure status.

BCRYPT_ALG_HANDLE bcrypt_alg = nullptr;
BCRYPT_KEY_HANDLE bcrypt_pub_key = nullptr;
NTSTATUS status = 0;

status = BCryptOpenAlgorithmProvider(
    &bcrypt_alg,
    BCRYPT_RSA_ALGORITHM,
    nullptr,
    0);

status = BCryptImportKeyPair(
    bcrypt_alg,
    nullptr,
    BCRYPT_PUBLIC_KEY_BLOB,
    &bcrypt_pub_key,
    reinterpret_cast<unsigned char *>(&rsa_pub_key),
    sizeof(rsa_pub_key),
    0);

BCRYPT_PKCS1_PADDING_INFO padding_info = { 0 };
ULONG output_size = 0;
status = BCryptDecrypt(
    bcrypt_pub_key,
    (PUCHAR)encrypted,
    (ULONG)encrypted_size,
    &padding_info,
    nullptr,
    0,
    nullptr,
    0,
    &output_size,
    BCRYPT_PAD_PKCS1);
if (!BCRYPT_SUCCESS(status)) {
    printf("Failed to decrypt, error 0x%xn", status);
    return false;
}

unsigned __int8 * decrypted = new unsigned __int8[output_size];

status = BCryptDecrypt(
    bcrypt_pub_key,
    (PUCHAR)encrypted,
    (ULONG)encrypted_size,
    &padding_info,
    nullptr,
    0,
    decrypted,
    output_size,
    &output_size,
    BCRYPT_PAD_PKCS1);
if (!BCRYPT_SUCCESS(status)) {
    printf("Failed to decrypt, error 0x%xn", status);
    return false;
}

...