feat: Add reference links to stellar files

Author: Keyur279

apps/stellar_app/stellar_context.h

@@ -32,6 +32,7 @@
 #define STELLAR_SIGNATURE_SIZE 64
 
 // Network passphrases
+// See https://developers.stellar.org/docs/learn/fundamentals/networks
 #define TESTNET_PASSPHRASE "Test SDF Network ; September 2015"
 #define MAINNET_PASSPHRASE "Public Global Stellar Network ; September 2015"
 
@@ -44,6 +45,7 @@ typedef struct {
 } stellar_config_t;
 
 // Stellar Memo types
+// See https://developers.stellar.org/docs/learn/encyclopedia/transactions-specialized/memos
 typedef enum {
   MEMO_NONE = 0,
   MEMO_TEXT = 1,
@@ -90,6 +92,7 @@ typedef enum {
  * 1. Creates a payload with account ID type (0x30) and the public key
  * 2. Calculates CRC16 checksum
  * 3. Encodes the result using base32
+ * See https://developers.stellar.org/docs/fundamentals-and-concepts/stellar-data-structures/accounts
  *
  * @param public_key The 32-byte ED25519 public key
  * @param address Buffer to store the resulting address (must be at least

apps/stellar_app/stellar_helpers.h

@@ -25,6 +25,8 @@
 
 #define STELLAR_IMPLICIT_ACCOUNT_DEPTH 3
 
+// BIP44 derivation path: m/44'/148'/n'
+// See https://github.com/satoshilabs/slips/blob/master/slip-0044.md
 #define STELLAR_PURPOSE_INDEX 0x8000002C    // 44'
 #define STELLAR_COIN_INDEX 0x80000094       // 148'
 #define STELLAR_ACCOUNT_INDEX 0x80000000    // 0'
@@ -47,6 +49,7 @@
  * 3, then this function return false indicating invalid derivation path. The
  * function supports checking derivation paths for HD wallets Types of
  * derivations: address: m/44'/148'/0'
+ * See https://developers.stellar.org/docs/fundamentals-and-concepts/accounts
  *
  * @param[in] path      The derivation path as an uint32 array
  * @param[in] levels     The number of levels in the derivation path

apps/stellar_app/stellar_pub_key.c

@@ -412,14 +412,19 @@ bool stellar_generate_address(const uint8_t *public_key, char *address) {
     return false;
   }
 
+  // Stellar address encoding (StrKey format)
+  // See https://github.com/stellar/stellar-protocol/blob/master/ecosystem/sep-0023.md
   uint8_t payload[35];
-  payload[0] = 6 << 3;    // Account ID type
+  payload[0] = 6 << 3;    // Account ID version byte (0x30)
   memcpy(payload + 1, public_key, 32);
 
+  // CRC16-XModem checksum calculation
+  // See https://stellar.stackexchange.com/questions/255/which-cryptographic-algorithm-is-used-to-generate-the-secret-and-public-keys
   uint16_t checksum = crc16(payload, 33);
   payload[33] = checksum & 0xFF;
   payload[34] = checksum >> 8;
 
+  // RFC4648 base32 encoding without padding
   base32_encode(payload, 35, address, 57, BASE32_ALPHABET_RFC4648);
   return true;
 }

apps/stellar_app/stellar_txn.c

@@ -490,6 +490,9 @@ static bool get_user_verification(void) {
   return true;
 }
 
+// See https://developers.stellar.org/docs/learn/encyclopedia/data-format/xdr
+// Envelope type (4 bytes) - ENVELOPE_TYPE_TX = 2
+// See https://github.com/stellar/stellar-protocol/blob/master/core/cap-0015.md
 static void write_uint32_be(uint8_t *buffer, uint32_t value) {
   buffer[0] = (value >> 24) & 0xFF;
   buffer[1] = (value >> 16) & 0xFF;

apps/stellar_app/stellar_txn_helpers.c

@@ -185,6 +185,8 @@ static int parse_memo_data(const uint8_t *xdr,
 }
 
 // Helper function 2: Parse operation data
+// Parse XDR transaction envelope format
+// See https://developers.stellar.org/docs/learn/encyclopedia/data-format/xdr
 static int parse_operation_data(const uint8_t *xdr,
                                 int *pos,
                                 int xdr_len,
@@ -257,6 +259,8 @@ int stellar_parse_transaction(const uint8_t *xdr,
   memset(payment, 0, sizeof(stellar_payment_t));
 
   // 1. Parse Envelope Type (4 bytes)
+  // ENVELOPE_TYPE_TX = 2 
+  // See https://github.com/stellar/stellar-protocol/blob/master/core/cap-0015.md
   uint32_t envelope_type = read_uint32_be_pos(xdr, &pos);
   if (envelope_type != 2) {
     return -1;