Use case: suspend/resume mode

Sequence diagram

Suspend/resume mode

@startuml participant "Application" as App participant "CRYP" as CRYP note over App,CRYP: CRYP initialization App -> CRYP: HAL_CRYP_Init() note over App,CRYP: Low priority block Encryption App -> CRYP: HAL_CRYP_Encrypt_IT() note over App,CRYP: Low priority process suspending App -> CRYP: HAL_CRYP_ProcessSuspend() App -> CRYP: HAL_CRYP_Suspend() note over App,CRYP: High priority process starting App -> CRYP: HAL_CRYP_Init() note over App,CRYP: Decrypt high priority block App -> CRYP: HAL_CRYP_Decrypt_IT() note over App,CRYP: Resume low priority block processing App -> CRYP: HAL_CRYP_Resume() @enduml

Code snippet

HAL1

HAL2 

/* Set the CRYP parameters */
hcryp.Instance = CRYP;

/* Set the CRYP parameters */
hcryp.Init.DataType = CRYP_BYTE_SWAP;
hcryp.Init.KeySize = CRYP_KEYSIZE_128B;
hcryp.Init.pKey     = AESKey128;
hcryp.Init.Algorithm = CRYP_AES_ECB;
HAL_CRYP_Init(&hcryp);

/* Low prio block Encryption */
HAL_CRYP_Encrypt_IT(&hcryp, Plaintext_8, 128, Encryptedtext);


/* request suspension */
HAL_CRYP_ProcessSuspend(&hcryp);


/* Suspend low prio block processing */
HAL_CRYP_Suspend(&hcryp);

/* -- Thread 1 released the CRYP peripheral and informed Thread 2 ---> */

















/* Resume low prio block processing */
HAL_CRYP_Resume(&hcryp);

/*  */








/* <--- Thread 2 asks to use the CRYP peripheral for a high-priority task -- */








/*  High priority block processing  */
/* Set the CRYP parameters */
hcryp.Init.DataType  = CRYP_BIT_SWAP;
hcryp.Init.KeySize   = CRYP_KEYSIZE_256B;
hcryp.Init.pKey      = AESKey256;
hcryp.Init.pInitVect = AESIV;
hcryp.Init.Algorithm = CRYP_AES_CTR;
HAL_CRYP_Init(&hcryp);

/*  Decrypt */
HAL_CRYP_Decrypt_IT(&hcryp, CiphertextAESCTR256_HighPrio,
                                                16, Decryptedtext_HighPrio);

/* <--- Thread 1 releases the CRYP peripheral so that the low-priority task can resume -- */

/* Set the CRYP parameters */
HAL_CRYP_Init(&hcryp,HAL_CRYP);
HAL_CRYP_AES_ECB_SetConfig(&hcryp);
HAL_CRYP_SetDataSwapping(&hcryp, HAL_CRYP_DATA_SWAPPING_BYTE);
HAL_CRYP_AES_SetNormalKey(&hcryp, HAL_CRYP_KEY_SIZE_128BIT, CRYPKey128);

/* Low prio block Encryption */
HAL_CRYP_Encrypt_IT(&hcryp, Plaintext_8, 128 , Encryptedtext);


/* request suspension */
HAL_CRYP_RequestSuspend(&hcryp);

/* --------------------- Wait for suspend callback -------------------*/

/* Suspend low prio block processing */
HAL_CRYP_SaveContext(&hcryp,&p_context);

/* -- Thread 1 released the CRYP peripheral and informed Thread 2 ---> */

















/* Restore process1 context */
HAL_CRYP_RestoreContext(&hcryp, &p_context);

/* Resume low prio block processing */
HAL_CRYP_Resume(&hcryp);

/*  */








/* <--- Thread 2 asks to use the CRYP peripheral for a high-priority task -- */








/*  High priority block processing  */
/* Set the CRYP parameters */
HAL_CRYP_AES_CTR_SetConfig(&hcryp,AESIV);
HAL_CRYP_SetDataSwapping(&hcryp, HAL_CRYP_DATA_SWAPPING_BIT);
HAL_CRYP_SetNormalKey(&hcryp, HAL_CRYP_KEY_SIZE_256BIT, AESKey256);



/*  Decrypt */
HAL_CRYP_Decrypt_IT(&hcryp, CiphertextAESCTR256_HighPrio,
                                              16, Decryptedtext_HighPrio);

/* --------------------- Wait for decrypt complete callback -------------------*/


/* <--- Thread 1 releases the CRYP peripheral so that the low-priority task can resume -- */

Key changes

  1. HAL2 provides explicit suspend and context management APIs: HAL_CRYP_RequestSuspend(), HAL_CRYP_SaveContext(), and HAL_CRYP_RestoreContext().

  2. HAL2 uses dedicated configuration functions for the algorithm, key and swapping (for example, HAL_CRYP_AES_ECB_SetConfig() and HAL_CRYP_AES_SetNormalKey()).