STMicroelectronics · parmi93 · Jun 16, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -19,19 +19,24 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **Platform AES API change** — all platform AES cryptographic functions now reference keys by secure storage index (`PLAT_UI32 key_idx`) instead of raw key pointer and length (`PLAT_UI8 *pKey, PLAT_UI16 key_length`). Affected functions: `stse_platform_aes_cmac_init`, `stse_platform_aes_cmac_compute`, `stse_platform_aes_cmac_verify`, `stse_platform_aes_cbc_enc`, `stse_platform_aes_cbc_dec`, `stse_platform_aes_ecb_enc`
 - **Renamed** `stsafea_open_host_session` to `stsafea_open_host_session_from_idx` — signature updated to accept key indices (`PLAT_UI32 host_MAC_key_idx`, `PLAT_UI32 host_cypher_key_idx`) instead of raw key pointers
 - **printf() calls replaced** with `stse_platform_printf()` in all library code to abstract away standard I/O and allow platform-specific implementations for logging and output
+- **Platform CRC API change** — introduces a context (`stse_crc16_context_t *`) parameter to make the CRC PAL APIs multi-context-safe. Affected functions: `stse_platform_Crc16_Accumulate` (PR [#90](https://github.com/STMicroelectronics/STSELib/pull/90))
 
 ### Added
 
 - `stse_platform_store_aes_key()` — new platform function to store an AES key into platform secure storage and retrieve its index
 - `stse_platform_delete_aes_key()` — new platform function to delete an AES key from platform secure storage by index
 - `stse_platform_printf()` — new platform function for formatted output, replacing all direct calls to `printf()` in the library with this abstraction to allow platform-specific implementations and avoid direct use of standard I/O in library code
+- `stse_platform_Crc16_ContextInit()` — new platform function to initialize a CRC16 context
+- `stse_platform_Crc16_ContextRelease()` — new platform function to release a CRC16 context
 
 ### Changed
+- `stse_platform_Crc16_Accumulate()` — Now it takes `stse_crc16_context_t *crc16_context` as param
 
 ### Deprecated
 
 ### Removed
 - `stsafea_open_host_session` function. Now replaced by `stsafea_open_host_session_from_idx` which accepts key indices instead of raw key pointers. Note that you must first store the AES keys in platform secure storage using `stse_platform_store_aes_key()` to obtain the required indices before opening a host session.
+- `stse_platform_Crc16_Calculate()` — Now replaced by `stse_platform_Crc16_ContextInit()` which doesn't calculate a CRC16 but initialize the CRC context which will be used to calculate the CRC via `stse_platform_Crc16_Accumulate()`.
 
 ### Fixed
 

diff --git a/core/stse_frame.c b/core/stse_frame.c
@@ -23,26 +23,32 @@
 #include "core/stse_frame.h"
 
 stse_ReturnCode_t stse_frame_crc16_compute(stse_frame_t *pFrame, PLAT_UI16 *pCrc) {
+    stse_ReturnCode_t ret;
     stse_frame_element_t *pCurrent_element;
+    stse_crc16_context_t crc_ctx;
 
     if (pFrame == NULL || pCrc == NULL) {
         return STSE_CORE_INCONSISTENT_FRAME;
     }
 
-    pCurrent_element = pFrame->first_element;
-    *pCrc = stse_platform_Crc16_Calculate(pCurrent_element->pData, pCurrent_element->length);
-    pCurrent_element = pCurrent_element->next;
-    while (pCurrent_element != NULL) {
-        if (pCurrent_element->length != 0) {
-            if (pCurrent_element->pData == NULL) {
-                return STSE_CORE_INCONSISTENT_FRAME;
+    ret = stse_platform_Crc16_ContextInit(&crc_ctx);
+    if (ret == STSE_OK) {
+        pCurrent_element = pFrame->first_element;
+        while (pCurrent_element != NULL) {
+            if (pCurrent_element->length != 0) {
+                if (pCurrent_element->pData == NULL) {
+                    ret = STSE_CORE_INCONSISTENT_FRAME;
+                    break;
+                }
+                *pCrc = stse_platform_Crc16_Accumulate(pCurrent_element->pData, pCurrent_element->length, &crc_ctx);
             }
-            *pCrc = stse_platform_Crc16_Accumulate(pCurrent_element->pData, pCurrent_element->length);
+            pCurrent_element = pCurrent_element->next;
         }
-        pCurrent_element = pCurrent_element->next;
+
+        stse_platform_Crc16_ContextRelease(&crc_ctx);
     }
 
-    return STSE_OK;
+    return ret;
 }
 
 void stse_frame_element_swap_byte_order(stse_frame_element_t *pElement) {

diff --git a/core/stse_platform.h b/core/stse_platform.h
@@ -33,6 +33,12 @@
 #include "core/stse_util.h"
 #include "stse_platform_generic.h"
 
+typedef struct stse_crc16_context_t stse_crc16_context_t;
+
+struct stse_crc16_context_t {
+	PLAT_UI16 value;
+};
+
 /*--------------------- STSAFE platform HAL functions --------------------------- */
 
 /*!
@@ -82,20 +88,37 @@ void stse_platform_printf(const char *format, ...);
 PLAT_UI32 stse_platform_generate_random(void);
 
 /*!
- * \brief      Compute a 16-bit crc value on specific 8-bit buffer of buffer length
- * \param[in]  pbuffer pointer to crc input buffer
- * \param[in]  length  input buffer length
- * \return     16-bit CRC value
+ * \brief Initializes a CRC16 context.
+ *
+ * Initializes the specified CRC16 context and prepares it for use with `stse_platform_Crc16_Accumulate()`.
+ * The same context instance shall be passed unchanged to all subsequent accumulation calls.
+ *
+ * \param[in]  crc16_context  Pointer to the CRC16 context to initialize.
+ * \return     \ref STSE_OK on success; \ref stse_ReturnCode_t error code otherwise.
  */
-PLAT_UI16 stse_platform_Crc16_Calculate(PLAT_UI8 *pbuffer, PLAT_UI16 length);
+stse_ReturnCode_t stse_platform_Crc16_ContextInit(stse_crc16_context_t *crc16_context);
 
 /*!
  * \brief      Accumulate an 8-bit buffer of buffer length in crc unit
- * \param[in]  pbuffer pointer to crc input buffer
- * \param[in]  length  input buffer length
+ * \param[in]  pbuffer      pointer to crc input buffer
+ * \param[in]  length       input buffer length
+ * \param[in]  crc16_context Pointer to the CRC context holder previously initialized successfully
+ * via `stse_platform_Crc16_ContextInit()`. This context is used internally to maintain the state
+ * required for incremental CRC computation across multiple calls to `stse_platform_Crc16_Accumulate()`.
  * \return     16-bit CRC value
  */
-PLAT_UI16 stse_platform_Crc16_Accumulate(PLAT_UI8 *pbuffer, PLAT_UI16 length);
+PLAT_UI16 stse_platform_Crc16_Accumulate(PLAT_UI8 *pbuffer, PLAT_UI16 length, 
+                                         stse_crc16_context_t *crc16_context);
+
+/*!
+ * \brief Releases resources associated with a CRC16 context.
+ * 
+ * Releases any resources allocated or acquired by `stse_platform_Crc16_ContextInit()`. Once 
+ * released, the context shall no longer be used unless it is reinitialized.
+ * 
+ * \param[in] crc16_context Pointer to a CRC context previously initialized with `stse_platform_Crc16_ContextInit()`.
+*/
+void stse_platform_Crc16_ContextRelease(stse_crc16_context_t *crc16_context);
 
 /*!
  * \brief      Perform a delay of "delay_val" ms

diff --git a/doc/resources/Markdown/04_PORTING_GUIDE/PAL_files/stse_platform_crc.c.md b/doc/resources/Markdown/04_PORTING_GUIDE/PAL_files/stse_platform_crc.c.md
@@ -11,26 +11,35 @@ The stse_platform_crc.c file provides CRC16 functions for the STSecureElement li
 
 <b> Implementation directives :</b> This abstaction function should implement or call a platform function/driver that perform CRC16 calculation process.
 
-## stse_platform_Crc16_Calculate:
+## stse_platform_Crc16_ContextInit:
 
-- Purpose: Calculates the CRC16 checksum for the given buffer.
+- Purpose: Initializes a CRC16 context.
 - Parameters:
-  - pbuffer: Pointer to the buffer.
-  - length: Length of the buffer.
-- Return Value: Returns the calculated CRC16 checksum.
+  - crc16_context: Pointer to the CRC16 context to initialize.
+- Return Value: Returns `STSE_OK` to indicate successful context initialization.
 
-<b> Implementation directives :</b> This abstaction function should implement or call a platform function/driver that perform CRC16 calculation process.
+<b> Implementation directives :</b> This abstraction function should implement or call a platform function/driver that perform CRC16 accumulate process.
 
 ## stse_platform_Crc16_Accumulate:
 
 - Purpose: Accumulates the CRC16 checksum for the given buffer.
 - Parameters:
   - pbuffer: Pointer to the buffer.
   - length: Length of the buffer.
+  - crc16_context: Pointer to the CRC context holder previously initialized successfully via `stse_platform_Crc16_ContextInit()`.
+    This context is used internally to maintain the state required for incremental CRC computation across multiple calls to `stse_platform_Crc16_Accumulate()`.
 - Return Value: Returns the accumulated CRC16 checksum.
 
 <b> Implementation directives :</b> This abstaction function should implement or call a platform function/driver that perform CRC16 acumulate process.
 
+## stse_platform_Crc16_ContextRelease:
+
+- Purpose: Releases resources associated with a CRC16 context.
+- Parameters:
+  - crc16_context: Pointer to a CRC context previously initialized with `stse_platform_Crc16_ContextInit()`.
+
+<b> Implementation directives :</b> This abstraction function should implement or call a platform function/driver that perform CRC16 accumulate process.
+
 Please find below an extract
 
 ```c
@@ -65,24 +74,53 @@ stse_ReturnCode_t stse_platform_crc16_init(void *pArg)
 }
 
 /**
- * \brief   Calculates the CRC16 checksum for the given buffer.
- * \param   pbuffer Pointer to the buffer.
- * \param   length  Length of the buffer.
- * \return  The calculated CRC16 checksum.
+ * \brief Initializes a CRC16 context.
+ *
+ * Initializes the specified CRC16 context and prepares it for use with `stse_platform_Crc16_Accumulate()`.
+ * The same context instance shall be passed unchanged to all subsequent accumulation calls.
+ *
+ * \param  crc16_context  Pointer to the CRC16 context to initialize.
+ * \return \ref STSE_OK on success; \ref stse_ReturnCode_t error code otherwise.
  */
-PLAT_UI16 stse_platform_Crc16_Calculate(PLAT_UI8 *pbuffer, PLAT_UI16 length)
+stse_ReturnCode_t stse_platform_Crc16_ContextInit(stse_crc16_context_t *crc16_context)
 {
-    return crc16_Calculate(pbuffer, length);
+    // If hardware CRC is used...
+    // mutex_lock() if the same CRC hardware module is used by multiple thread
+    __HAL_CRC_DR_RESET(&stm32_crc_hal);
+
+    // or just initialize the context if CRC computation is done in software
+    crc16_context->value = (PLAT_UI16)0xFFFF;
 }
 
 /**
  * \brief   Accumulates the CRC16 checksum for the given buffer.
- * \param   pbuffer Pointer to the buffer.
- * \param   length  Length of the buffer.
+ * \param   pbuffer       Pointer to the buffer.
+ * \param   length        Length of the buffer.
+ * \param   crc16_context Pointer to the CRC context holder previously initialized successfully
+ * via `stse_platform_Crc16_ContextInit()`. This context is used internally to maintain the state
+ * required for incremental CRC computation across multiple calls to `stse_platform_Crc16_Accumulate()`.
  * \return  The accumulated CRC16 checksum.
  */
-PLAT_UI16 stse_platform_Crc16_Accumulate(PLAT_UI8 *pbuffer, PLAT_UI16 length)
+PLAT_UI16 stse_platform_Crc16_Accumulate(PLAT_UI8 *pbuffer, PLAT_UI16 length, 
+                                         stse_crc16_context_t *crc16_context);
+{
+    // If hardware CRC computation is used...
+    return ~HAL_CRC_Accumulate(&stm32_crc_hal, (uint32_t *)pbuffer, length);
+
+    // If software CRC computation is used...
+    return crc16_Accumulate(pbuffer, length, crc16_context);
+}
+
+/**
+ * \brief Releases resources associated with a CRC16 context.
+ * 
+ * Releases any resources allocated or acquired by `stse_platform_Crc16_ContextInit()`. Once 
+ * released, the context shall no longer be used unless it is reinitialized.
+ * 
+ * \param crc16_context Pointer to a CRC context previously initialized with `stse_platform_Crc16_ContextInit()`.
+*/
+void stse_platform_Crc16_ContextRelease(stse_crc16_context_t *crc16_context)
 {
-    return crc16_Accumulate(pbuffer, length);
+    // mutex_unlock() if the same CRC hardware module is used by multiple thread
 }
 ```
diff --git a/services/stsafea/stsafea_frame_transfer.c b/services/stsafea/stsafea_frame_transfer.c
@@ -219,22 +219,28 @@ stse_ReturnCode_t stsafea_frame_receive(stse_Handle_t *pSTSE, stse_frame_t *pFra
         /* ====================================================== */
         /* ====== compute CRC for response without payload ====== */
 
-        computed_crc = stse_platform_Crc16_Calculate(&received_header, STSE_RSP_FRAME_HEADER_SIZE);
+        stse_crc16_context_t crc_ctx;
+        ret = stse_platform_Crc16_ContextInit(&crc_ctx);
+        if (ret == STSE_OK) {
+            computed_crc = stse_platform_Crc16_Accumulate(&received_header, STSE_RSP_FRAME_HEADER_SIZE, &crc_ctx);
+
+            stse_platform_Crc16_ContextRelease(&crc_ctx);
 
+            /* - Verify CRC */
+            if (computed_crc != ((received_crc[0] << 8) + received_crc[1])) {
+                ret = STSE_SERVICE_FRAME_CRC_ERROR;
+            } else {
+                ret = (stse_ReturnCode_t)(received_header & STSE_STSAFEA_RSP_STATUS_MASK);
+            }
+        }
+
 #ifdef STSE_FRAME_DEBUG_LOG
         stse_platform_printf("\n\r STSAFE Frame <  (%d-byte) : { 0x%02X } { 0x%02X 0x%02X }\n\r",
                              received_length + STSE_FRAME_CRC_SIZE,
                              received_header,
                              received_crc[0],
                              received_crc[1]);
 #endif /* STSE_FRAME_DEBUG_LOG */
-
-        /* - Verify CRC */
-        if (computed_crc != ((received_crc[0] << 8) + received_crc[1])) {
-            return (STSE_SERVICE_FRAME_CRC_ERROR);
-        }
-
-        ret = (stse_ReturnCode_t)(received_header & STSE_STSAFEA_RSP_STATUS_MASK);
     } else {
         /* ======================================================= */
         /* ====== Format the frame to handle CRC and filler ====== */