Version v0.2.91 - Menu changes

README.md

@@ -1,6 +1,47 @@
 # OTP Cipher - One Time Pad Implementation
 
-A secure one-time pad (OTP) cipher implementation in C with automatic versioning system.
+
+## Introduction
+
+A secure one-time pad (OTP) cipher implementation in C.
+
+## Why One-Time Pads
+
+Nostr and much of the web runs on public key cryptography. Public key cryptography is great, but it is vulnerable. Cryptographers know this, and they know what it takes to attack it, so what they do is just make the keys large enough such that the system is resistant to attack given computers as they are today.
+
+There is one type of cryptography, however, that is invulnerable to any type of attack in our universe, and that is known as a one-time pad.
+
+One-time pads rely directly on the laws of physics and what it means for a number to be truly random.
+
+If you take your secret message and mix it with truly random numbers, and don't use those random numbers again, then that message is unbreakable by any computer, no matter how powerful, quantum or not, forever.
+
+In fact, one-time pads are so powerful that if you have data encrypted by a one-time pad located in a distant galaxy, and that data is not kept anywhere else, then by destroying the pad used for encryption in your galaxy, the data is wiped from the universe and can never be recovered.
+
+## Advantages and Limitations
+
+### Limitations
+
+1. The pad must be shared between the parties wanting to use it.
+2. The pad must be as long or longer than what you want to encrypt, and it can't be used a second time.
+
+### Modern Advantages
+
+While in the past, pad length might have been a problem, readily available USB drives in the terabytes make size less of a problem for many uses.
+
+We are also becoming very accustomed to YubiKey authenticators in the USB ports of our computers. A small USB drive in our devices can now easily contain a key of greater length than all the text messages we would expect to send over a lifetime.
+
+### Multi-Device Coordination
+
+One of the problems to address is the fact that to use an OTP across several devices means that they have to coordinate to know when they are encrypting new plaintext and where to start in the key. Reusing the same section of the pad, while not necessarily fatal, degrades the encryption from its status as "Information Theoretically Secure".
+
+To address this problem, we can use Nostr to share among devices the place in the pad that was last left off.
+
+### Additional Benefits
+
+One-time pads can be trivially encrypted and decrypted using pencil and paper, making them accessible even without electronic devices.
+
+
+
 
 ## Features
 
@@ -13,15 +54,6 @@ A secure one-time pad (OTP) cipher implementation in C with automatic versioning
 - **Multiple Build Options**: Standard and static linking builds
 - **Cross-Platform**: Works on Linux and other UNIX-like systems
 
-## Version Information
-
-This project uses an automatic versioning system that:
-- Automatically increments the patch version on each build
-- Embeds build timestamp, git commit hash, and branch information
-- Creates git tags for version tracking
-- Generates version header files with detailed build metadata
-
-Current version can be viewed with: `./otp --help` or by running the interactive mode.
 
 ## Building
 
@@ -31,7 +63,7 @@ Current version can be viewed with: `./otp --help` or by running the interactive
 - Git (for version tracking)
 - Make
 
-**Note: OpenSSL is no longer required! This implementation is now completely self-contained.**
+
 
 ### Build Commands
 

TODO.md

@@ -0,0 +1,25 @@
+# TODO
+
+
+## Change technique for adding keyboard entropy.
+
+## Some of the processing seems similar, so maybe code could be more compact.
+
+
+## There is the problem of the location of the pad revealing metadata about how many messages have been sent in the past, or at least the size of the messsages.
+
+One solution could be to start the pad at a random location, and then wrap around, so an attacker could never tell the size of the past text sent.  This helps. But then you have to store the start location, which you could do within the header of the pad along with the pad?
+
+Or, better yet, assume the offset is a very large size, and use the pad itself to encrypt the offset. 
+
+## Take a look at how the file header is being handled.
+
+## We have three different decrypt file functions
+
+
+
+## Setup for multiple USB drives
+
+
+## Change back in pad menu to exit
+

otp.c

@@ -131,6 +131,16 @@ void get_directory_display(const char* file_path, char* result, size_t result_si
 
 void print_usage(const char* program_name);
 
+
+
+////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+//      MAIN
+////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+
+
+
 int main(int argc, char* argv[]) {
     // Load preferences first
     load_preferences();
@@ -234,13 +244,71 @@ int command_line_mode(int argc, char* argv[]) {
         return generate_pad_with_entropy(size, 1, 0);  // No keyboard entropy for command line
     }
     else if (strcmp(argv[1], "encrypt") == 0 || strcmp(argv[1], "-e") == 0) {
-        if (argc < 3 || argc > 4) {
+        if (argc < 2 || argc > 4) {
-            printf("Usage: %s encrypt|-e <pad_chksum_or_prefix> [text_to_encrypt]\n", argv[0]);
+            printf("Usage: %s encrypt|-e [pad_chksum_or_prefix] [text_to_encrypt]\n", argv[0]);
             return 1;
         }
-        // Pass text if provided, otherwise NULL for interactive mode
+        
-        const char* text = (argc == 4) ? argv[3] : NULL;
+        // Check if pad was specified or use default
-        return encrypt_text(argv[2], text);
+        const char* pad_identifier = NULL;
+        const char* text = NULL;
+        
+        if (argc == 2) {
+            // Just -e, use default pad, no text (interactive)
+            pad_identifier = NULL;
+            text = NULL;
+        } else if (argc == 3) {
+            // Could be -e <pad> or -e <text> (using default pad)
+            // Check if default pad is available to determine interpretation
+            char* default_pad = get_default_pad_path();
+            if (default_pad) {
+                // Default pad available, treat argument as text
+                pad_identifier = NULL;
+                text = argv[2];
+                free(default_pad);
+            } else {
+                // No default pad, treat as pad identifier
+                pad_identifier = argv[2];
+                text = NULL;
+            }
+        } else {
+            // argc == 4: -e <pad> <text>
+            pad_identifier = argv[2];
+            text = argv[3];
+        }
+        
+        // If pad_identifier is NULL, we need to use default pad
+        if (pad_identifier == NULL) {
+            char* default_pad = get_default_pad_path();
+            if (default_pad) {
+                // Extract checksum from default pad path
+                char* filename = strrchr(default_pad, '/');
+                if (!filename) filename = default_pad;
+                else filename++; // Skip the '/'
+                
+                // Extract checksum (remove .pad extension)
+                if (strlen(filename) >= 68 && strstr(filename, ".pad")) {
+                    static char default_checksum[65];
+                    strncpy(default_checksum, filename, 64);
+                    default_checksum[64] = '\0';
+                    pad_identifier = default_checksum;
+                }
+                free(default_pad);
+                
+                // Call encrypt_text and then comment about using default pad
+                int result = encrypt_text(pad_identifier, text);
+                if (result == 0) {
+                    printf("# Used default pad: %.16s...\n", pad_identifier);
+                }
+                return result;
+            } else {
+                printf("Error: No default pad configured. Specify pad explicitly or configure default pad.\n");
+                return 1;
+            }
+        } else {
+            // Explicit pad specified, normal operation
+            return encrypt_text(pad_identifier, text);
+        }
     }
     else if (strcmp(argv[1], "decrypt") == 0 || strcmp(argv[1], "-d") == 0) {
         if (argc == 2) {
@@ -329,11 +397,11 @@ void show_main_menu(void) {
 
     printf("\n\n\n\n=========================== Main Menu - OTP %s ===========================\n\n", get_version() );
 
-    printf(" \033[4mT\033[0mext encrypt\n");
+    printf(" \033[4mT\033[0mext encrypt\n");    //TEXT ENCRYPT
-    printf(" \033[4mF\033[0mile encrypt\n");
+    printf(" \033[4mF\033[0mile encrypt\n");    //FILE ENCRYPT
-    printf(" \033[4mD\033[0mecrypt\n");
+    printf(" \033[4mD\033[0mecrypt\n");         //DECRYPT
-    printf(" \033[4mP\033[0mads\n");
+    printf(" \033[4mP\033[0mads\n");            //PADS
-    printf(" E\033[4mx\033[0mit\n");
+    printf(" E\033[4mx\033[0mit\n");            //EXIT
     printf("\nSelect option: ");
 }
 
@@ -807,9 +875,27 @@ int list_available_pads(void) {
     struct dirent* entry;
     int count = 0;
     
+    // Get current default pad path for comparison
+    char* current_default = get_default_pad_path();
+    char default_pad_checksum[65] = "";
+    
+    if (current_default) {
+        // Extract checksum from default pad path
+        char* filename = strrchr(current_default, '/');
+        if (!filename) filename = current_default;
+        else filename++; // Skip the '/'
+        
+        // Extract checksum (remove .pad extension)
+        if (strlen(filename) >= 68 && strstr(filename, ".pad")) {
+            strncpy(default_pad_checksum, filename, 64);
+            default_pad_checksum[64] = '\0';
+        }
+        free(current_default);
+    }
+    
     printf("\nAvailable pads:\n");
-    printf("%-4s %-20s %-12s %-12s %-8s\n", "No.", "ChkSum", "Size", "Used", "% Used");
+    printf("%-4s %-7s %-20s %-12s %-12s %-8s\n", "No.", "Default", "ChkSum", "Size", "Used", "% Used");
-    printf("%-4s %-20s %-12s %-12s %-8s\n", "---", "-------------------", "----------", "----------", "------");
+    printf("%-4s %-7s %-20s %-12s %-12s %-8s\n", "---", "-------", "-------------------", "----------", "----------", "------");
     
     while ((entry = readdir(dir)) != NULL) {
         if (strstr(entry->d_name, ".pad") && strlen(entry->d_name) == 68) {
@@ -818,6 +904,10 @@ int list_available_pads(void) {
             strncpy(chksum, entry->d_name, 64);
             chksum[64] = '\0';
             
+            // Check if this is the default pad
+            int is_default = (strlen(default_pad_checksum) > 0 &&
+                             strncmp(chksum, default_pad_checksum, 64) == 0);
+            
             // Get pad file size
             char full_path[1024]; // Increased buffer size to accommodate longer paths
             snprintf(full_path, sizeof(full_path), "%s/%s", current_pads_dir, entry->d_name);
@@ -855,7 +945,7 @@ int list_available_pads(void) {
                 // Calculate percentage
                 double percentage = (double)used_bytes / st.st_size * 100.0;
                 
-                printf("%-4d %-20.16s %-12s %-12s %.1f%%\n", count, chksum, size_str, used_str, percentage);
+                printf("%-4d %-7s %-20.16s %-12s %-12s %.1f%%\n", count, is_default ? "*" : "", chksum, size_str, used_str, percentage);
             }
         }
     }
@@ -2617,7 +2707,54 @@ int load_preferences(void) {
     
     FILE* file = fopen(preferences_file, "r");
     if (!file) {
-        return 0; // No preferences file, use defaults
+        // No preferences file exists - create it and set first pad as default
+        
+        // Create .otp directory if it doesn't exist
+        struct stat st = {0};
+        if (stat(preferences_dir, &st) == -1) {
+            if (mkdir(preferences_dir, 0755) != 0) {
+                return 1;
+            }
+        }
+        
+        // Find the first available pad to set as default
+        DIR* dir = opendir(current_pads_dir);
+        if (dir) {
+            struct dirent* entry;
+            char first_pad_path[1024];
+            int found_pad = 0;
+            
+            while ((entry = readdir(dir)) != NULL && !found_pad) {
+                if (strstr(entry->d_name, ".pad") && strlen(entry->d_name) == 68) {
+                    // Found a pad file - construct full absolute path
+                    char absolute_path[1024];
+                    if (current_pads_dir[0] == '/') {
+                        // Already absolute path
+                        snprintf(first_pad_path, sizeof(first_pad_path), "%s/%s", current_pads_dir, entry->d_name);
+                    } else {
+                        // Relative path - make it absolute
+                        char current_dir[512];
+                        if (getcwd(current_dir, sizeof(current_dir))) {
+                            snprintf(first_pad_path, sizeof(first_pad_path), "%s/%s/%s", current_dir, current_pads_dir, entry->d_name);
+                        } else {
+                            // Fallback to relative path
+                            snprintf(first_pad_path, sizeof(first_pad_path), "%s/%s", current_pads_dir, entry->d_name);
+                        }
+                    }
+                    strncpy(default_pad_path, first_pad_path, sizeof(default_pad_path) - 1);
+                    default_pad_path[sizeof(default_pad_path) - 1] = '\0';
+                    found_pad = 1;
+                }
+            }
+            closedir(dir);
+            
+            // Create the preferences file with the default pad
+            if (found_pad) {
+                save_preferences();
+            }
+        }
+        
+        return 0; // Successfully initialized
     }
     
     char line[1024];
@@ -2717,7 +2854,29 @@ char* get_default_pad_path(void) {
 }
 
 int set_default_pad_path(const char* pad_path) {
-    return set_preference("default_pad", pad_path);
+    if (!pad_path) {
+        return set_preference("default_pad", NULL);
+    }
+    
+    // Ensure we store the full absolute path
+    char absolute_path[1024];
+    if (pad_path[0] == '/') {
+        // Already absolute path
+        strncpy(absolute_path, pad_path, sizeof(absolute_path) - 1);
+        absolute_path[sizeof(absolute_path) - 1] = '\0';
+    } else {
+        // Relative path - make it absolute
+        char current_dir[512];
+        if (getcwd(current_dir, sizeof(current_dir))) {
+            snprintf(absolute_path, sizeof(absolute_path), "%s/%s", current_dir, pad_path);
+        } else {
+            // Fallback to using the path as-is if getcwd fails
+            strncpy(absolute_path, pad_path, sizeof(absolute_path) - 1);
+            absolute_path[sizeof(absolute_path) - 1] = '\0';
+        }
+    }
+    
+    return set_preference("default_pad", absolute_path);
 }
 
 // OTP thumb drive detection function implementation
@@ -3443,7 +3602,7 @@ int handle_pads_menu(void) {
         printf("No pads found.\n");
         printf("\nOptions:\n");
         printf(" \033[4mG\033[0menerate new pad\n");
-        printf(" \033[4mB\033[0mack to main menu\n");
+        printf(" E\033[4mx\033[0mit\n");
         printf("\nSelect option: ");
         
         char input[10];
@@ -3491,18 +3650,41 @@ int handle_pads_menu(void) {
         prefixes[i][prefix_lengths[i]] = '\0';
     }
     
-    // Display pads with minimal prefixes underlined
+    // Display pads with minimal prefixes underlined and default indicator
     printf("\nAvailable pads:\n");
-    printf("%-8s %-12s %-12s %-12s %-8s\n", "ChkSum", "Dir", "Size", "Used", "% Used");
+    printf("%-7s %-8s %-12s %-12s %-12s %-8s\n", "Default", "ChkSum", "Dir", "Size", "Used", "% Used");
-    printf("%-8s %-12s %-12s %-12s %-8s\n", "--------", "------------", "----------", "----------", "------");
+    printf("%-7s %-8s %-12s %-12s %-12s %-8s\n", "-------", "--------", "------------", "----------", "----------", "------");
+    
+    // Get current default pad path for comparison
+    char* current_default = get_default_pad_path();
+    char default_pad_checksum[65] = "";
+    
+    if (current_default) {
+        // Extract checksum from default pad path
+        char* filename = strrchr(current_default, '/');
+        if (!filename) filename = current_default;
+        else filename++; // Skip the '/'
+        
+        // Extract checksum (remove .pad extension)
+        if (strlen(filename) >= 68 && strstr(filename, ".pad")) {
+            strncpy(default_pad_checksum, filename, 64);
+            default_pad_checksum[64] = '\0';
+        }
+        free(current_default);
+    }
     
     for (int i = 0; i < pad_count; i++) {
+        // Check if this is the default pad
+        int is_default = (strlen(default_pad_checksum) > 0 &&
+                         strncmp(pads[i].chksum, default_pad_checksum, 64) == 0);
+        
         // Display first 8 characters of checksum with prefix underlined
         char checksum_8char[9];
         strncpy(checksum_8char, pads[i].chksum, 8);
         checksum_8char[8] = '\0';
         
-        printf("\033[4m%.*s\033[0m%s %-12s %-12s %-12s %.1f%%\n",
+        printf("%-7s \033[4m%.*s\033[0m%s %-12s %-12s %-12s %.1f%%\n",
+               is_default ? "*" : "",             // Default indicator
                prefix_lengths[i], checksum_8char,  // Underlined prefix
                checksum_8char + prefix_lengths[i], // Rest of 8-char checksum
                pads[i].location,                   // Use the stored location info
@@ -3513,7 +3695,8 @@ int handle_pads_menu(void) {
     
     printf("\nActions:\n");
     printf(" \033[4mG\033[0menerate new pad\n");
-    printf(" \033[4mB\033[0mack to main menu\n");
+    printf(" \033[4mS\033[0met default pad\n");
+    printf(" E\033[4mx\033[0mit\n");
     printf("\nSelect pad (by prefix) or action: ");
     
     char input[MAX_HASH_LENGTH];
@@ -3531,8 +3714,61 @@ int handle_pads_menu(void) {
             return handle_pads_menu();
         }
         return result;
-    } else if (toupper(input[0]) == 'B') {
+    } else if (toupper(input[0]) == 'S') {
-        return 0; // Back to main menu
+        // Set default pad
+        printf("\nSelect pad to set as default (by prefix): ");
+        char pad_input[MAX_HASH_LENGTH];
+        if (!fgets(pad_input, sizeof(pad_input), stdin)) {
+            printf("Error: Failed to read input\n");
+            return 1;
+        }
+        pad_input[strcspn(pad_input, "\n")] = 0;
+        
+        // Find matching pad by prefix using the same logic as pad selection
+        int matched_pad = -1;
+        int match_count = 0;
+        
+        for (int i = 0; i < pad_count; i++) {
+            if (strncmp(pad_input, pads[i].chksum, strlen(pad_input)) == 0) {
+                matched_pad = i;
+                match_count++;
+            }
+        }
+        
+        if (match_count == 0) {
+            printf("No pad found matching prefix '%s'\n", pad_input);
+            return handle_pads_menu();
+        } else if (match_count > 1) {
+            printf("Ambiguous prefix. Multiple matches found.\n");
+            return handle_pads_menu();
+        }
+        
+        // Construct the full absolute pad path and set as default
+        char new_default_path[1024];
+        if (current_pads_dir[0] == '/') {
+            // Already absolute path
+            snprintf(new_default_path, sizeof(new_default_path), "%s/%s.pad", current_pads_dir, pads[matched_pad].chksum);
+        } else {
+            // Relative path - make it absolute
+            char current_dir[512];
+            if (getcwd(current_dir, sizeof(current_dir))) {
+                snprintf(new_default_path, sizeof(new_default_path), "%s/%s/%s.pad", current_dir, current_pads_dir, pads[matched_pad].chksum);
+            } else {
+                // Fallback to relative path
+                snprintf(new_default_path, sizeof(new_default_path), "%s/%s.pad", current_pads_dir, pads[matched_pad].chksum);
+            }
+        }
+        
+        if (set_default_pad_path(new_default_path) == 0) {
+            printf("Default pad set to: %.16s...\n", pads[matched_pad].chksum);
+            printf("Full path: %s\n", new_default_path);
+        } else {
+            printf("Error: Failed to update default pad preference\n");
+        }
+        
+        return handle_pads_menu();
+    } else if (toupper(input[0]) == 'X') {
+        return 0; // Exit to main menu
     }
     
     // Find matching pad by prefix
@@ -3715,7 +3951,7 @@ void print_usage(const char* program_name) {
     printf("Usage:\n");
     printf("  %s                                         - Interactive mode\n", program_name);
     printf("  %s generate|-g <size>                      - Generate new pad\n", program_name);
-    printf("  %s encrypt|-e <pad_checksum_prefix> [text] - Encrypt text\n", program_name);
+    printf("  %s encrypt|-e [pad_checksum_prefix] [text] - Encrypt text\n", program_name);
     printf("  %s decrypt|-d [encrypted_message]          - Decrypt message\n", program_name);
     printf("  %s -f <file> <pad_prefix> [-a] [-o <out>]  - Encrypt file\n", program_name);
     printf("  %s list|-l                                 - List available pads\n", program_name);