Added a cx_crc32() function

The implementation of cx_crc32_hw() on Ledger devices is buggy and produces incorrect CRC32 checks. Ledger are fixing cx_crc32_hw() on each device either through SDK or OS updates but until then cx_crc32() can be used.

CHANGELOG.md

@@ -1,8 +1,10 @@
 # Change log
 
-## [1.5.5] - 2023-12-10
+## [1.6.0] - 2024-01-14
 ### Added
 - Use CX_CHECK macro in compare_recovery_phrase()
+- Added a `cx_crc32()` function
+  - The implementation of `cx_crc32_hw()` on Ledger devices is buggy and produces incorrect CRC32 checks. Ledger are fixing `cx_crc32_hw()` on each device either through SDK or OS updates but until then `cx_crc32()` can be used.
 
 ### Changed
 -

Makefile

@@ -27,8 +27,8 @@ all: default
 
 APPNAME = "Seed Tool"
 APPVERSION_M = 1
-APPVERSION_N = 5
-APPVERSION_P = 5
+APPVERSION_N = 6
+APPVERSION_P = 0
 APPVERSION   = "$(APPVERSION_M).$(APPVERSION_N).$(APPVERSION_P)"
 
 APP_LOAD_PARAMS = --appFlags 0x10 $(COMMON_LOAD_PARAMS) --curve secp256k1 --path ""

README.md

@@ -20,11 +20,22 @@
 
 Use the utilities provided by this Ledger application to check a backed up seed or generate [Shamir's Secret Sharing (SSS)](https://en.wikipedia.org/wiki/Shamir%27s_secret_sharing) for a seed.
 
+Not all Ledger devices are equal. The older, less capable devices do not have the capacity to provide a full range of seed utilities. The following table lists the seed utilities provided by each devices type:
+<div align="center">
+
+||Nano S|Nano S+|Nano X|Stax|
+| :--- | :---: | :---: | :---: | :---: |
+|[Check BIP39](#check-bip39)|$${\color{green}✓}$$|$${\color{green}✓}$$|$${\color{green}✓}$$|$${\color{green}✓}$$|
+|[Check Shamir's secret shares](#check-shamirs-secret-shares)|$${\color{green}✓}$$|$${\color{green}✓}$$|$${\color{green}✓}$$|$${\color{green}✓}$$|
+|[Generate Shamir's secret sharing](#generate-shamirs-secret-sharing)|$${\color{green}✓}$$|$${\color{green}✓}$$|$${\color{green}✓}$$|$${\color{green}✓}$$|
+|[Generate BIP85](#generate-bip85)|$${\color{red}✗}$$|$${\color{green}✓}$$|$${\color{green}✓}$$|$${\color{green}✓}$$|
+</div>
+
 ## Check BIP39
 The application invites the user to type a [BIP-39](https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki) mnemonic on their Ledger device. The BIP-39 mnemonic is compared to the onboarded seed and the application notifies the user whether both seeds match or not.
 
 ## Generate Shamir's secret sharing
-When the seed is validated, the user can create [Shamir's secret sharing (SSS)](https://en.wikipedia.org/wiki/Shamir%27s_secret_sharing) from the BIP-39 phrase that they provided.
+If the user provided seed is valid and matches the onboarded seed, the user can create [Shamir's secret sharing (SSS)](https://en.wikipedia.org/wiki/Shamir%27s_secret_sharing) from their BIP-39 phrase.
 The application uses [Sharded Secret Key Reconstruction (SSKR)](https://github.com/BlockchainCommons/Research/blob/master/papers/bcr-2020-011-sskr.md), an interoperable implementation of [Shamir's Secret Sharing (SSS)](https://en.wikipedia.org/wiki/Shamir%27s_secret_sharing). This provides a way for you to divide or 'shard' the master seed underlying a Bitcoin HD wallet into 'shares', which you can then distribute to friends, family, or fiduciaries. If you lose your seed, you can reconstruct it by collecting a sufficient number of your shares (the 'threshold'). Knowledge of fewer than the required number of parts ensures that information about the master secret is not leaked.
 
 * SSKR is round-trip compatible with BIP-39.
@@ -66,7 +77,7 @@ flowchart LR
         1.1 --> 1.2.1[Enter 12 Words] --> 1.3{Validate BIP39 Phrases}
         1.1 --> 1.2.2[Enter 18 Words] --> 1.3
         1.1 --> 1.2.3[Enter 24 Words] --> 1.3
-        1.3 --> |Valid BIP39| 1.4
+        1.3 --> |Matching BIP39| 1.4
         1.3 --> |Invalid BIP39| 1.3.1[Quit]
         subgraph 1.4[Generate SSKR Shares]
             direction TB

src/ux_common/onboarding_seed_sskr.c

@@ -8,12 +8,32 @@
 #include "common_bip39.h"
 #include "sskr.h"
 
+// NOTE:
+// The implementation of cx_crc32_hw() on Ledger devices is buggy and produces incorrect CRC32
+// checks. Ledger are fixing cx_crc32_hw() on each device either through SDK or OS updates.
+// The following function is a temporary workaround that can be removed once cx_crc32_hw()
+// works on all Ledger devices
+
+uint32_t cx_crc32(const uint8_t *data, size_t len) {
+    uint32_t crc = ~0;
+    const uint8_t *end = data + len;
+
+    while (data < end) {
+        crc ^= *data++;
+        for (uint8_t i = 0; i < 8; i++) {
+            uint32_t mask = ~((crc & 1) - 1);
+            crc = (crc >> 1) ^ (0xEDB88320 & mask);
+        }
+    }
+    return ~crc;
+}
+
 // Returns the CRC-32 checksum of the input buffer in network byte order (big endian).
 uint32_t cx_crc32_hw_nbo(const uint8_t *bytes, size_t len) {
 #if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
-    return cx_crc32_hw(bytes, len);
+    return cx_crc32(bytes, len);
 #elif __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-    return os_swap_u32(cx_crc32_hw(bytes, len));
+    return os_swap_u32(cx_crc32(bytes, len));
 #else
 #error "What kind of system is this?"
 #endif