Print payment addresses instead of viewing keys for shielded transaction inputs

[murisi]

Currently the Ledger app displays shielded transaction inputs as extended full viewing keys. Displaying extended full viewing keys takes many screens and increases signing time because each screen transition have a lag. Therefore instead of printing the extended full viewing key that owns a shielded input, we would now like to display the payment address at which the shielded input was received (in both normal and expert mode). This should be shorter, needs less screens to display, and may be more recognizable to end-users (since they would have had to have distribute that payment address prior to receiving tokens at it). This payment address is computed using the shielded input's diversifier and its note's diversified transmission key, see: namada-net/namada#4436 . Please see attached test vectors containing the intended displays: testvecs-fmted.json.gz and testdbgs.txt.gz.

[murisi]

Probably something like the patch below could make the above test vectors pass. It concatenates the input's payment address diverisifer with the input's diversified transmission key to make a payment address, and then it bech32 encodes that. This is done for normal shielded transfers, IBC transfers, and IBC NFT transfers.

diff --git a/app/src/parser_print_txn.c b/app/src/parser_print_txn.c
index 02278d5..85a98dc 100644
--- a/app/src/parser_print_txn.c
+++ b/app/src/parser_print_txn.c
@@ -231,8 +231,11 @@ static __attribute__((noinline)) parser_error_t printTransferTxn( const parser_c
     bytes_t namount = {0};
     uint8_t amount_denom = 0;
     const char* symbol = NULL;
+    const uint8_t *diversifier = NULL;
     const uint8_t *stoken = NULL;
     const uint8_t *rtoken = NULL;
+    const uint8_t *pk_d = NULL;
+    uint8_t tmp_payment_addr[DIVERSIFIER_LEN + PKD_LEN] = {0};
     masp_asset_data_t asset_data = {0};
     uint32_t asset_idx = 0;
     const uint8_t *amount = {0};
@@ -261,8 +264,10 @@ static __attribute__((noinline)) parser_error_t printTransferTxn( const parser_c
         displayIdx -= spendsStart;
         for(uint32_t i = 0; i < n_spends; i++) {
             getSpendfromIndex(i, &spend);
+            diversifier = spend.ptr + EXTENDED_FVK_LEN;
             stoken = spend.ptr + EXTENDED_FVK_LEN + DIVERSIFIER_LEN;
             amount = spend.ptr + EXTENDED_FVK_LEN + DIVERSIFIER_LEN + ASSET_ID_LEN;
+            pk_d = spend.ptr + EXTENDED_FVK_LEN + DIVERSIFIER_LEN + ASSET_ID_LEN + sizeof(uint64_t) + GD_LEN;
             CHECK_ERROR(findAssetData(&ctx->tx_obj->transaction.sections.maspBuilder, stoken, &asset_data, &asset_idx))
 
             if (displayIdx >= (asset_data.symbol == NULL ? 3 : 2)) {
@@ -356,7 +361,9 @@ static __attribute__((noinline)) parser_error_t printTransferTxn( const parser_c
             break;
         case 7:
             snprintf(outKey, outKeyLen, "Sender");
-            CHECK_ERROR(crypto_encodeLargeBech32(spend.ptr, EXTENDED_FVK_LEN, (uint8_t*) tmp_buf, sizeof(tmp_buf), 0));
+            MEMCPY(tmp_payment_addr, diversifier, DIVERSIFIER_LEN);
+            MEMCPY(tmp_payment_addr + DIVERSIFIER_LEN, pk_d, PKD_LEN);
+            CHECK_ERROR(crypto_encodeLargeBech32(tmp_payment_addr, PAYMENT_ADDR_LEN, (uint8_t*) tmp_buf, sizeof(tmp_buf), 1));
             pageString(outVal, outValLen, (const char*) tmp_buf, pageIdx, pageCount);
 
             break;
@@ -1422,8 +1429,11 @@ static __attribute__((noinline)) parser_error_t printIBCTxn( const parser_contex
     bytes_t namount = {0};
     uint8_t amount_denom = 0;
     const char* symbol = NULL;
+    const uint8_t *diversifier = NULL;
     const uint8_t *stoken = NULL;
     const uint8_t *rtoken = NULL;
+    const uint8_t *pk_d = NULL;
+    uint8_t tmp_payment_addr[DIVERSIFIER_LEN + PKD_LEN] = {0};
     masp_asset_data_t asset_data = {0};
     uint32_t asset_idx = 0;
     const uint8_t *amount = {0};
@@ -1456,8 +1466,10 @@ static __attribute__((noinline)) parser_error_t printIBCTxn( const parser_contex
         displayIdx -= spendsStart;
         for(uint32_t i = 0; i < n_spends; i++) {
             getSpendfromIndex(i, &spend);
+            diversifier = spend.ptr + EXTENDED_FVK_LEN;
             stoken = spend.ptr + EXTENDED_FVK_LEN + DIVERSIFIER_LEN;
             amount = spend.ptr + EXTENDED_FVK_LEN + DIVERSIFIER_LEN + ASSET_ID_LEN;
+            pk_d = spend.ptr + EXTENDED_FVK_LEN + DIVERSIFIER_LEN + ASSET_ID_LEN + sizeof(uint64_t) + GD_LEN;
             CHECK_ERROR(findAssetData(&ctx->tx_obj->transaction.sections.maspBuilder, stoken, &asset_data, &asset_idx))
 
             if (displayIdx >= (asset_data.symbol == NULL ? 3 : 2)) {
@@ -1613,7 +1625,9 @@ static __attribute__((noinline)) parser_error_t printIBCTxn( const parser_contex
             break;
         case 15:
             snprintf(outKey, outKeyLen, "Sender");
-            CHECK_ERROR(crypto_encodeLargeBech32(spend.ptr, EXTENDED_FVK_LEN, (uint8_t*) tmp_buf, sizeof(tmp_buf), 0));
+            MEMCPY(tmp_payment_addr, diversifier, DIVERSIFIER_LEN);
+            MEMCPY(tmp_payment_addr + DIVERSIFIER_LEN, pk_d, PKD_LEN);
+            CHECK_ERROR(crypto_encodeLargeBech32(tmp_payment_addr, PAYMENT_ADDR_LEN, (uint8_t*) tmp_buf, sizeof(tmp_buf), 1));
             pageString(outVal, outValLen, (const char*) tmp_buf, pageIdx, pageCount);
 
             break;
@@ -1785,8 +1799,11 @@ static __attribute__((noinline)) parser_error_t printNFTIBCTxn( const parser_con
     bytes_t namount = {0};
     uint8_t amount_denom = 0;
     const char* symbol = NULL;
+    const uint8_t *diversifier = NULL;
     const uint8_t *stoken = NULL;
     const uint8_t *rtoken = NULL;
+    const uint8_t *pk_d = NULL;
+    uint8_t tmp_payment_addr[DIVERSIFIER_LEN + PKD_LEN] = {0};
     masp_asset_data_t asset_data = {0};
     uint32_t asset_idx = 0;
     const uint8_t *amount = {0};
@@ -1826,8 +1843,10 @@ static __attribute__((noinline)) parser_error_t printNFTIBCTxn( const parser_con
         displayIdx -= spendsStart;
         for(uint32_t i = 0; i < n_spends; i++) {
             getSpendfromIndex(i, &spend);
+            diversifier = spend.ptr + EXTENDED_FVK_LEN;
             stoken = spend.ptr + EXTENDED_FVK_LEN + DIVERSIFIER_LEN;
             amount = spend.ptr + EXTENDED_FVK_LEN + DIVERSIFIER_LEN + ASSET_ID_LEN;
+            pk_d = spend.ptr + EXTENDED_FVK_LEN + DIVERSIFIER_LEN + ASSET_ID_LEN + sizeof(uint64_t) + GD_LEN;
             CHECK_ERROR(findAssetData(&ctx->tx_obj->transaction.sections.maspBuilder, stoken, &asset_data, &asset_idx))
 
             if (displayIdx >= (asset_data.symbol == NULL ? 3 : 2)) {
@@ -1986,7 +2005,9 @@ static __attribute__((noinline)) parser_error_t printNFTIBCTxn( const parser_con
             break;
         case 16:
             snprintf(outKey, outKeyLen, "Sender");
-            CHECK_ERROR(crypto_encodeLargeBech32(spend.ptr, EXTENDED_FVK_LEN, (uint8_t*) tmp_buf, sizeof(tmp_buf), 0));
+            MEMCPY(tmp_payment_addr, diversifier, DIVERSIFIER_LEN);
+            MEMCPY(tmp_payment_addr + DIVERSIFIER_LEN, pk_d, PKD_LEN);
+            CHECK_ERROR(crypto_encodeLargeBech32(tmp_payment_addr, PAYMENT_ADDR_LEN, (uint8_t*) tmp_buf, sizeof(tmp_buf), 1));
             pageString(outVal, outValLen, (const char*) tmp_buf, pageIdx, pageCount);
 
             break;
diff --git a/app/src/parser_txdef.h b/app/src/parser_txdef.h
index 8708e5e..54b1163 100644
--- a/app/src/parser_txdef.h
+++ b/app/src/parser_txdef.h
@@ -48,6 +48,7 @@ extern "C" {
 #define DIVERSIFIER_LEN 11
 #define ALPHA_LEN 32
 #define MEMO_LEN 512
+#define GD_LEN 32
 #define PKD_LEN 32
 #define PAYMENT_ADDR_LEN (DIVERSIFIER_LEN + PKD_LEN)
 #define OVK_LEN 32

[murisi]

Please find attached an expanded set (10,000 entries) of test vectors.

vectors-fmt.json.gz