Does mbedtls APIs (sha256.h) use the hardware acceleration?

Question

Hello Nordic team, 
 I'm currently looking into mbedtls on nRF5340, I'm using nRF NCS SDK 2.1.0 
 I wanted to calculate the HASH of the firmware image, I already developed one API that calculate and provide me a HASH of firmware image, But I am unsure that API internally used the nRF5340 hardware acceleration feature or not? If not, then please provide me a sample code that used the hardware-acceleration internally? Below is my API that provide me a HASH of firmware image. 
 
 void calculate_file_hash ( unsigned char * hash_value , size_t hash_size ) 
 { 
 uint8_t buffer [ READ_FLASH_BYTES ]; 
 size_t bytes_read , address = QSPI_OTA_HEADER_START_ADDRESS ; 
 int rc = 0u ; 
 
 LOG_INF ( "calculate_file_hash" ); 
 
 mbedtls_sha256_context sha256_ctx ; 
 mbedtls_sha256_init ( & sha256_ctx ); 
 mbedtls_sha256_starts ( & sha256_ctx , /*is224=*/ 0 ); 
 
 for(bytes_read = 210539; bytes_read > 0; ) // For Net core 
 { 
 if ( bytes_read >= READ_FLASH_BYTES ) 
 { 
 rc = external_flash_sector_read ( address , buffer , READ_FLASH_BYTES ); 
 if ( rc != 0U ) 
 { 
 LOG_INF ( "Error in flash reading( %x )" , rc ); 
 } 
 mbedtls_sha256_update ( & sha256_ctx , buffer , READ_FLASH_BYTES ); 
 } 
 else 
 { 
 memset ( buffer , 0xFF , READ_FLASH_BYTES ); 
 rc = external_flash_sector_read ( address , buffer , bytes_read ); 
 if ( rc != 0U ) 
 { 
 LOG_INF ( "Error in flash reading( %x )" , rc ); 
 } 
 mbedtls_sha256_update ( & sha256_ctx , buffer , bytes_read ); 
 } 
 if ( bytes_read >= READ_FLASH_BYTES ) 
 { 
 bytes_read = bytes_read - READ_FLASH_BYTES ; 
 } 
 else 
 { 
 bytes_read = 0 ; 
 } 
 address = address + READ_FLASH_BYTES ; 
 // LOG_INF("address = %x, bytes_read = %d", address, bytes_read); 
 } 
 
 mbedtls_sha256_finish ( & sha256_ctx , hash_value ); 
 mbedtls_sha256_free ( & sha256_ctx ); 
 } 
 
 Thanks in advance, 
 Kaushik

dejans · Accepted Answer

Hi, I have reproduced your issue. There are some changes which you could make to enable successful building of your project. Here are required configuration changes in prj.conf: CONFIG_NORDIC_SECURITY_BACKEND=y
#CONFIG_CC3XX_BACKEND=y 
CONFIG_MBEDTLS_SHA256_C=y 
#CONFIG_PSA_CRYPTO_DRIVER_CC3XX I have added an overlay file in Kconfig fragments, but this is not mandatory for having successful builds: -DCONF_OVERLAY:STRING="board/nrf5340dk_nrf5340_cpuapp.overlay" I have also built lock sample with the shield by adding these Kconfig fragments: -DCONF_OVERLAY:STRING="board/nrf5340dk_nrf5340_cpuapp.overlay"
-Dhci_rpmsg_SHIELD:STRING="nrf7002_ek_coex" In both cases builds were successful. As a confirmation of activated hardware acceleration, CONFIG_MBEDTLS_SHA256_ALT=y was present in build\zephyr\.conf file. Best regards, Dejan

Does mbedtls APIs (sha256.h) use the hardware acceleration?

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