Here's a short example how to generate a HMAC SHA256 hash (via passphrase). It's good to "sign" messages as a passphrase is used to hash a message,
Taken from: https://techtutorialsx.com/2018/01/25/esp32-arduino-applying-the-hmac-sha-256-mechanism/
Globals:
Payload ("the message") can be longer. I just have set it to 255.
Code:
Helper to check the hash: https://www.freeformatter.com/hmac-generator.html#ad-output
Supported digest's:
Change the constant or use another varaible in Globals to use it by parameter. Change the size of the hashcode variable, too (e.g. 64 bytes for sha512)
Taken from: https://techtutorialsx.com/2018/01/25/esp32-arduino-applying-the-hmac-sha-256-mechanism/
Globals:
B4X:
Public hmackey(255) As Byte
Public hmackey_len As ULong
Public hmacpayload(255) As Byte
Public hmacpayload_len As ULong
Public hmacbytes(32) As BytePayload ("the message") can be longer. I just have set it to 255.
Code:
B4X:
Sub Hmac
Dim s As String="secretKey"
bc.ArrayCopy2(s,0,hmackey,0,s.Length)
hmackey_len=s.Length
Dim s As String="Hello HMAC SHA 256!"
bc.ArrayCopy2(s,0,hmacpayload,0,s.Length)
hmacpayload_len=s.Length
RunNative("GenHmac", Null)
Log(bc.HexFromBytes(hmacbytes))
End Sub
#if c
#include "mbedtls/md.h"
void GenHmac (B4R::Object* o) {
mbedtls_md_context_t ctx;
mbedtls_md_type_t md_type = MBEDTLS_MD_SHA256;
mbedtls_md_init(&ctx);
mbedtls_md_setup(&ctx, mbedtls_md_info_from_type(md_type), 1);
mbedtls_md_hmac_starts(&ctx, (unsigned char *)b4r_main::_hmackey->data, b4r_main::_hmackey_len);
mbedtls_md_hmac_update(&ctx, (unsigned char *)b4r_main::_hmacpayload->data, b4r_main::_hmacpayload_len);
mbedtls_md_hmac_finish(&ctx, (unsigned char *)b4r_main::_hmacbytes->data);
mbedtls_md_free(&ctx);
}
#End IfHelper to check the hash: https://www.freeformatter.com/hmac-generator.html#ad-output
Supported digest's:
Change the constant or use another varaible in Globals to use it by parameter. Change the size of the hashcode variable, too (e.g. 64 bytes for sha512)
B4X:
MBEDTLS_MD_NONE
None.
MBEDTLS_MD_MD2
The MD2 message digest.
MBEDTLS_MD_MD4
The MD4 message digest.
MBEDTLS_MD_MD5
The MD5 message digest.
MBEDTLS_MD_SHA1
The SHA-1 message digest.
MBEDTLS_MD_SHA224
The SHA-224 message digest.
MBEDTLS_MD_SHA256
The SHA-256 message digest.
MBEDTLS_MD_SHA384
The SHA-384 message digest.
MBEDTLS_MD_SHA512
The SHA-512 message digest.
MBEDTLS_MD_RIPEMD160
The RIPEMD-160 message digest.