Save modified array in function

Question

I found a problem. It seems like I always did it in this way, but I know something is wrong and I can't find what. In main I initialize 3 char arrays (array of destination to file to read data, an array of destination to file to write data, and modifier); params is a 2D array (getting list of command-line arguments) and initialize it

int main(int argc,char**argv) {
    char** params;
    params = (int**)malloc(argc - 1 * sizeof(int*));
    for (int i = 1; i < argc; i++) {
        params[i - 1] = (int*)malloc(strlen(argv[i]) * sizeof(int));
    }
    char* inputFile = malloc(sizeof(char));
    char* outputFile = malloc(sizeof(char));
    char* key = malloc(sizeof(char));
    CheckParams(params,argc,argv);
    if (!ValidateInput(params,inputFile,outputFile,key,argc)) {
        return -1;
    }

СheckParams is a function that modifies params array to command-line arguments(this one works fine, I modify my array in a function, and it keep modified in main)

void CheckParams(char** params, int argc, char** argv) {
    for (int i = 1; i < argc; i++) {
        for (int j = 0; j < strlen(argv[i]); j++) {
            params[i - 1][j] = argv[i][j];
        }
        params[i - 1][strlen(argv[i])] = '\0';
    }
}

Then I wrote a function ValidateInput, that have to modify those 3 arrays(inputFile, outputFile, and Key). This function those contains a bit of validation

int ValidateInput(char** params,char* inputFile, char* outputFile, char* key, int argc) {
    if (argc >= 4) {
        if (strcmp(params[0],"-i")==0 && strcmp(params[2],"-o")==0) {
            inputFile = realloc(inputFile, sizeof(char) * strlen(params[1]) + 1 );
            for (int i = 0; i < strlen(params[1]); i++) {
                inputFile[i] = params[1][i];
            }
            inputFile[strlen(params[1])] = '\0';
            outputFile = realloc(outputFile, sizeof(char) * strlen(params[3]) + 1 );
            for (int i = 0; i < strlen(params[3]); i++) {
                outputFile[i] = params[3][i];
            }
            outputFile[strlen(params[3])] = '\0';
            if (argc >= 5) {
                key = realloc(key, sizeof(char) * strlen(params[4]) + 1 );
                for (int i = 0; i < strlen(params[4]); i++) {
                    key[i] = params[4][i];
                }
                key[strlen(params[4])] = '\0';
            }
            else {
                key = realloc(key, sizeof(char) * 8);
                key = "default";
            }
            return 1;
        }
        else {
            return 0;
        }
    }
    else {
        return 0;
    }
}

Maybe I'm so dumb and tired and i cant find so obvious error, but the most interesting thing, that inside ValidateInput function everything works correct, but after returning to main , inputFile and outputFile are garbage, BUT key feels good, just like params. So where is a problem. Ty for help