2.5.2.4 Crypto_Aead_AesGcm_Final

crypto_Aead_Status_E Crypto_Aead_AesGcm_Final(
    st_crypto_Aead_AesGcm_Ctx *ptr_aesGcmCtx_st, 
    uint8_t *ptr_authTag, 
    uint32_t authTagLen
    );

Description

This API is used to obtain the authentication tag for AES-GCM encryption. To use it, first initialize the context by calling the Crypto_Aead_AesGcm_Init function. If additional authentication data (AAD) is required, add it using the Crypto_Aead_AesGcm_AddAadData call; otherwise, skip this API call. Then, proceed with ciphering the data using Crypto_Aead_AesGcm_Cipher. Finally, call this API to get the authentication tag.

Parameters


No.	Argument Type	Argument Name	Type	Description
1	st_Crypto_Aead_AesGcm_ctx*	ptr_aesGcmCtx_st	Input	AES-GCM Algorithm context
2	uint8_t*	ptr_authTag	Output/Input	Pointer to store authentication tag value
3	uint8_t*	authTagLen	Input	Authentication tag length in bytes, range 12-16 bytes

Returns


Return Type	Description
crypto_Aead_Status_E	Function returns the status of the API.

Prerequisites

To use the HW handler, the algorithm must be enabled in Crypto v4 in MPLAB® Code Configurator.
To use the SW handler, the algorithm must be enabled in wolfCrypt, and linked to Crypto V4 in MPLAB® Code Configurator.
Crypto_Aead_AesGcm_Init, Crypto_Aead_AesGcm_Cipher, Crypto_Aead_AesGcm_AddAadData and must be called prior to calling Crypto_Aead_AesGcm_Final.

Example

#define sessionID 1
crypto_Aead_Status_E status;
crypto_HandlerType_E handlerType_en = CRYPTO_HANDLER_HW_INTERNAL;
crypto_CipherOper_E cipherOper_en = CRYPTO_CIOP_ENCRYPT;
st_Crypto_Aead_AesGcm_ctx AesGcm_ctx;
uint8_t inputData[32] = {/*data*/};
uint32_t dataLen = sizeof(inputData);
uint8_t key[32] = {/*data*/};
uint32_t keyLen = sizeof(key);
uint8_t outData[64];
uint8_t initVect[32] = {/*data*/};
uint32_t initVectLen = sizeof(initVect);
uint8_t authTag[32];
uint32_t authTagLen = 16; // auth tag length of 12-16 bytes
uint8_t aad[32] = {/*data*/};
uint32_t aadLen = sizeof(aad);

status = Crypto_Aead_AesGcm_Init(
    &AesGcm_ctx,
    handlerType_en,
    cipherOper_en,
    key,
    keyLen,
    initVect,
    initVectLen,
    sessionID
    ); 

status = Crypto_Aead_AesGcm_Cipher(
    &AesGcm_ctx,
    inputData,
    dataLen,
    outData
    );

status =  Crypto_Aead_AesGcm_AddAadData(
    &AesGcm_ctx,
    aad,    
    aadLen
    );

status = Crypto_Aead_AesGcm_Final(
    &AesGcm_ctx,
    authTag,
    authTagLen
    );