Here's nother example how to use RSA on a ESP32 based on this documentation:
https://tls.mbed.org/kb/how-to/encrypt-and-decrypt-with-rsa
Notes:
- If the filesystem does not work, you need to format it with fs.format once.
- I've just copied the Public and Private Key from another app
- Both keys are written to file and then loaded with the mbed methods
- You can - of course - create keys by code (which is recommended). See the docs for it.
- See my and other examples how to use RSA
- The length of data to be en- and decrypted is limited by the algorythm (see the general RSA docs for it)
Create new keys:
I use a Windows *bat file to do this via Apache/OpenSSL (I have installed it via XAMPP). This is compatible with most platforms (B4x, PHP, .net, etc.)
B4R Code (no lib needed as mbed tls is included in the github repository you download to install everything for the ESP32)
https://tls.mbed.org/kb/how-to/encrypt-and-decrypt-with-rsa
Notes:
- If the filesystem does not work, you need to format it with fs.format once.
- I've just copied the Public and Private Key from another app
- Both keys are written to file and then loaded with the mbed methods
- You can - of course - create keys by code (which is recommended). See the docs for it.
- See my and other examples how to use RSA
- The length of data to be en- and decrypted is limited by the algorythm (see the general RSA docs for it)
Create new keys:
I use a Windows *bat file to do this via Apache/OpenSSL (I have installed it via XAMPP). This is compatible with most platforms (B4x, PHP, .net, etc.)
B4X:
cd C:\xampp\apache\bin
openssl genrsa -out PrivateKey.pem 2048
openssl pkcs8 -topk8 -inform pem -in PrivateKey.pem -outform pem -nocrypt -out C:\Users\Klaus\Desktop\PrivateKey.pem
pauseB4R Code (no lib needed as mbed tls is included in the github repository you download to install everything for the ESP32)
B4X:
#Region Project Attributes
#AutoFlushLogs: True
#CheckArrayBounds: True
#StackBufferSize: 50000
#DefineExtra: #define SKIP_B4RNEW
#End Region
Sub Process_Globals
Public Serial1 As Serial
Private fs As ESP8266FileSystem
Public bc As ByteConverter 'not needed
End Sub
Private Sub AppStart
Serial1.Initialize(115200)
Log("*** B4R AppStart ***")
If Not(fs.Initialize()) Then
Log("Unable to initialize File System")
Return
End If
Log("File System successfully initialized")
'Write Public Key to file
fs.OpenReadWrite("/our-key.pub")
Dim PubKey As String = JoinStrings(Array As String("-----BEGIN PUBLIC KEY-----", CRLF , "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAmRdtXAQR/AN82QQmcGIt", CRLF , "JofGKgTEescayQshjA2Co+tVHRl10cUqUiTg9MxZe2S5rIlWU5qEB+pmDX3eXrAz", CRLF , "oGfvTf1V0qok1fRAPV8QAzJc7qAEUr+ryC3BokQ/0cD6ijmvPg8qv1fPl+jcviDn", CRLF , "sUVdkq34dYaQDDybpXamt2sPsi5O2w+/zXglzrzB2+SITABWn3FNnHElQkJOYpOM", CRLF , "Kf3vI6oRlLOjvsCaYqvmxSg4CTzWdc9trzS8dwVh/MXFuhdi6huwpM3p6ZHfWURm", CRLF , "9BThtx9MKB7N289/zrAkylOXeIGwgqJuP56gLwgJGlZmY9rZiXRoAsZheMpM13+b", CRLF , "bQIDAQAB", CRLF , "-----END PUBLIC KEY-----"))
Log("Pub: ",bc.HexFromBytes(PubKey))
Dim buffer() As Byte = bc.StringToBytes(PubKey)
fs.Stream.WriteBytes(buffer, 0, buffer.Length)
fs.Stream.Flush
fs.Close
Log("Pub Key written...")
'Write Private Key to file
fs.OpenReadWrite("/our-key.pem")
Dim PrivKey As String = JoinStrings(Array As String("-----BEGIN PRIVATE KEY-----", CRLF , "MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQCZF21cBBH8A3zZ", CRLF , "BCZwYi0mh8YqBMR6xxrJCyGMDYKj61UdGXXRxSpSJOD0zFl7ZLmsiVZTmoQH6mYN", CRLF , "fd5esDOgZ+9N/VXSqiTV9EA9XxADMlzuoARSv6vILcGiRD/RwPqKOa8+Dyq/V8+X", CRLF , "6Ny+IOexRV2Srfh1hpAMPJuldqa3aw+yLk7bD7/NeCXOvMHb5IhMAFafcU2ccSVC", CRLF , "Qk5ik4wp/e8jqhGUs6O+wJpiq+bFKDgJPNZ1z22vNLx3BWH8xcW6F2LqG7Ckzenp", CRLF , "kd9ZRGb0FOG3H0woHs3bz3/OsCTKU5d4gbCCom4/nqAvCAkaVmZj2tmJdGgCxmF4", CRLF , "ykzXf5ttAgMBAAECggEBAIqqv7HTNf8RoapoqfCt3LvDy+kPfHDBnC9yV6amLikP", CRLF , "5n5/K0sgzh6trN3Po1WzfMMdewYrNWB+HoYl9p/J9llbC1WXHH+/AbKSlQWB790V", CRLF , "Zzv10TSqzIx7daLnMu9pXwaJDYSm9E9w2GZ+1EObRoI5lHJiBmVdx2huFYWgnY4Q", CRLF , "kvRkEalL4IJ2IA1wl6J6zwOH3bWNDtsAz2Z6J5lHyto34/RpRwiLhlBweECR1pJS", CRLF , "AcYuTXFVrhOeFbvrZkJzXsz9KdpFUbwqj1XrcnSmsck2VCVyXUESruVzErqQltZe", CRLF , "uRDEP21oKkQFWg3boVycvwtWrEnFPJ/xs2k0o5wWeUECgYEAyDTwBDSNxL8S7x+A", CRLF , "iMtbUBbjXgs7aNGVkswnxWAg0KqdX1su/uL3nSlPGfX/Hoa95T8jHaDp2nZYSszV", CRLF , "IwBBMQF7GCcMh3BmI3/Xz4y7ZVb4r2xmb/nZTQ4o/wqZSMjbgbvz2AVVNDHbTsJ7", CRLF , "SXY5rfxH1f5cgBR5sC88J+nIG+UCgYEAw8E2gMIRFpppYJY8sVGpbXugtGIatLC1", CRLF , "P9G4h0l4LJs7nq1iWO/6oZffS6bpLbDgNcqOqXjUBFwg03+pfwT2ohah3mqjiaBW", CRLF , "goXvmrjfrXE5tJvSO2C4O8+d9qMt1s8v3HfrPtXzn2FH61DFFzxprKpgYLfBhAw3", CRLF , "7RtTJTox2OkCgYAsfbco+BTZOC0Y/sMtoyNztOJqL8zQCmNW8A+WiTpBpOi8HCNh", CRLF , "eUbVoix19Hjxa7gfjdxb5TqS1eHhHYvv70qNfWrBf0wFfTD1ip+G/BtY9e7l7Q0G", CRLF , "rVthCFiL9OsDhb9iIUabJvQ8WSgHZKjJNoCy7XF5WMFtpR81zAluRUG3EQKBgQC0", CRLF , "4HcICknX5N2xzaBPB/HRpAYeJvgeNZmEWrhy6UQNk3JHcFYLb9LaNYayVIvpGCJU", CRLF , "EdI4bdkaHjaGttNa9q8dnmP7K/XoWSsWd8Op52Fm1dRIOiLLktcpDPIczzKv5cmH", CRLF , "oZbQ/MibYDwgBwXWLpBGZzeepqw84z1Z7YGqSFd+4QKBgAveGZ6TZeqD6vdkckpR", CRLF , "cqkU7rwH6n+JXuttQOEcIo+BSVGk79MbJF/IvWpTqZNCz78F5c+UWaG4SXT8zyYA", CRLF , "+AXaWyIo2alxLiuRi9xihsVf27VMcs6/GXdJN75OZiRoE/W+QCwVfu3iKM/l1xpN", CRLF , "k6jYCK4WvnJR3QYImYpiW7CG", CRLF , "-----END PRIVATE KEY-----"))
Dim buffer2() As Byte = bc.StringToBytes(PrivKey)
fs.Stream.WriteBytes(buffer2, 0, buffer2.Length)
fs.Stream.Flush
fs.Close
Log("Priv Key written...")
'List files
For Each f As File In fs.ListFiles("/")
Log(f.Name)
Next
RunNative("RSA", Null)
End Sub
#if C
#include <mbedtls/aes.h>
#include "mbedtls/md.h"
#include "mbedtls/pk.h"
#include "mbedtls/ctr_drbg.h"
#include "mbedtls/entropy.h"
unsigned char encrypted[MBEDTLS_MPI_MAX_SIZE];
unsigned char decrypted[MBEDTLS_MPI_MAX_SIZE];
void RSA (B4R::Object* o) {
memset(encrypted, 0, sizeof(encrypted));
memset(decrypted, 0, sizeof(decrypted));
int ret = 0;
mbedtls_pk_context pk;
mbedtls_pk_init( &pk );
/*
* Read the RSA public key
*/
if( ( ret = mbedtls_pk_parse_public_keyfile( &pk, "/spiffs/our-key.pub" ) ) != 0 )
{
printf( " failed\n ! mbedtls_pk_parse_public_keyfile returned -0x%04x\n", -ret );
char errbuf[256];
mbedtls_strerror( ret, errbuf, 200 );
mbedtls_printf("Last error was: -0x%04x - %s\n\n", (int) -ret, errbuf );
}
printf("Pub Key loaded...\n");
size_t olen = 0;
unsigned char to_encrypt[] = "This is a test..";
size_t to_encrypt_len = sizeof(to_encrypt);
mbedtls_ctr_drbg_context ctr_drbg;
char *personalization = "my_app_specific_string";
mbedtls_entropy_context entropy;
mbedtls_entropy_init( &entropy );
mbedtls_ctr_drbg_init( &ctr_drbg );
ret = mbedtls_ctr_drbg_seed( &ctr_drbg , mbedtls_entropy_func, &entropy,
(const unsigned char *) personalization,
strlen( personalization ) );
if( ( ret = mbedtls_pk_encrypt( &pk, to_encrypt, to_encrypt_len,
encrypted, &olen, sizeof(encrypted),
mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
{
printf( " failed\n ! mbedtls_pk_encrypt returned -0x%04x\n", -ret );
char errbuf[256];
mbedtls_strerror( ret, errbuf, 200 );
mbedtls_printf("Last error was: -0x%04x - %s\n\n", (int) -ret, errbuf );
}
printf("Encrypted...\n");
printf("encrypted: %i \n", sizeof(encrypted));
printf("Olen: %i \n", olen);
int i;
for( i = 0; i < 256; i++ )
{
printf( "%02x[%c]%c", encrypted[i], (encrypted[i]>31)?encrypted[i]:' ', ((i&0xf)!=0xf)?' ':'\n' );
}
printf( "\n" );
//Decrypt
//int ret = 0;
//mbedtls_pk_context pk1;
mbedtls_pk_init( &pk );
/*
* Read the RSA privatekey
*/
if( ( ret = mbedtls_pk_parse_keyfile( &pk, "/spiffs/our-key.pem", "" ) ) != 0 )
{
printf( " failed\n ! mbedtls_pk_parse_keyfile returned -0x%04x\n", -ret );
}
printf("Priv Key loaded...\n");
//olen = 0;
//unsigned char decrypted[1024];
/*
* Calculate the RSA encryption of the data.
*/
printf( "\n . Decrypting...\n" );
fflush( stdout );
printf("encrypted: %i \n", sizeof(encrypted));
printf("Olen: %i \n", olen);
printf("Decrypted: %i \n", sizeof(decrypted));
printf("1024: %i \n", 1024);
if( ( ret = mbedtls_pk_decrypt( &pk, encrypted, olen, decrypted, &olen, sizeof(decrypted),
mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
{
printf( " failed\n ! mbedtls_pk_decrypt returned -0x%04x\n", -ret );
}
printf("Decrypted...\n");
printf("Decrypted Text: %s \n", decrypted);
for( i = 0; i < 128; i++ )
{
printf( "%02x[%c]%c", decrypted[i], (decrypted[i]>31)?decrypted[i]:' ', ((i&0xf)!=0xf)?' ':'\n' );
}
printf( "\n" );
}
#End if