Article no.5: rename iOS, improve graphs, clarify descriptions

_posts/2024-01-23-research-update-5.md

@@ -5,7 +5,7 @@ author: ["Christian Reitter"]
 date: 2024-01-23 17:00:00 +0000
 ---
 
-Last Friday, we learned of a [newly disclosed vulnerability](https://secbit.io/blog/en/2024/01/19/trust-wallets-fomo3d-summer-vuln/) in the `Trust Wallet` software which is relevant to Milk Sad. Researchers from [SECBIT Labs](https://secbit.io) tracked down an older wallet generation weakness in the IOS platform version of `Trust Wallet` from 2018 and connected it to the large thefts on 2023-07-12 that triggered our Milk Sad research.<br/>
+Last Friday, we learned of a [newly disclosed vulnerability](https://secbit.io/blog/en/2024/01/19/trust-wallets-fomo3d-summer-vuln/) in the `Trust Wallet` software which is relevant to Milk Sad. Researchers from [SECBIT Labs](https://secbit.io) tracked down an older wallet generation weakness in the iOS platform version of `Trust Wallet` from 2018 and connected it to the large thefts on 2023-07-12 that triggered our Milk Sad research.<br/>
 Using the newly available information, we managed to reproduce some of their findings, and can give a first look at additional data we collected.
 
 <div id="toc-container" markdown="1">
@@ -18,7 +18,7 @@ Using the newly available information, we managed to reproduce some of their fin
 
 ## Vulnerability TL;DR
 
-Open source code shows that [a core component](https://github.com/trustwallet/trezor-crypto-ios/commits/master/) of the `Trust Wallet` app for IOS generated new cryptocurrency wallets using unsafe functions in the `trezor-crypto` library that were not meant for production. As a result, their wallet entropy is based on a weak PRNG with 32-bit state that is seeded with easy-to-guess time values. This makes all wallets generated with vulnerable app versions easy to brute force remotely, like the weak `bx seed` mechanism in Libbitcoin. Both weaknesses were attacked on-chain at the same time in July 2023.
+Open source code shows that [a core component](https://github.com/trustwallet/trezor-crypto-ios/commits/master/) of the `Trust Wallet` app for iOS generated new cryptocurrency wallets using unsafe functions in the `trezor-crypto` library that were not meant for production. As a result, their wallet entropy is based on a weak PRNG with 32-bit state that is seeded with easy-to-guess time values. This makes all wallets generated with vulnerable app versions easy to brute force remotely, like the weak `bx seed` mechanism in Libbitcoin. Both weaknesses were attacked on-chain at the same time in July 2023.
 
 If you want to understand this better, we recommend taking a look at the [Trust Wallet's Fomo3D Summer: Fresh Discovery of Low Entropy Flaw From 2018](https://secbit.io/blog/en/2024/01/19/trust-wallets-fomo3d-summer-vuln/) disclosure of the SECBIT team.
 
@@ -31,8 +31,8 @@ The newly disclosed vulnerability comes in two forms. Together with the previous
 | Issue | When | Characteristics | Research |
 | -- | -- | -- | -- | -- | -- | -- |
 | vulnerable Trust Wallet browser extension | 2022/2023 | Mersenne Twister based | [research update #2]({% link _posts/2023-12-06-research-update-2.md %}) |
-| vulnerable Trust Wallet IOS app - **variant A** | Mid-2018 | `LCG16807` `MINSTD_RAND0` + `trezor-crypto` [2e528be](https://github.com/trezor/trezor-crypto/commit/2e528be1e91dd48c0e55061fbdd40ccf8b285559) | this article |
-| vulnerable Trust Wallet IOS app - **variant B** | Mid-2018 | `LCG16807` `MINSTD_RAND0` + `trezor-crypto` [009850](https://github.com/trezor/trezor-crypto/commit/009850f6c9afcf60b4c6280afd46868b1a7a1fdd) | this article |
+| vulnerable Trust Wallet iOS app - **variant A** | Mid-2018 | `LCG16807` `MINSTD_RAND0` + `trezor-crypto` [2e528be](https://github.com/trezor/trezor-crypto/commit/2e528be1e91dd48c0e55061fbdd40ccf8b285559) | this article |
+| vulnerable Trust Wallet iOS app - **variant B** | Mid-2018 | `LCG16807` `MINSTD_RAND0` + `trezor-crypto` [009850](https://github.com/trezor/trezor-crypto/commit/009850f6c9afcf60b4c6280afd46868b1a7a1fdd) | this article |
 
 Each weak PRNGs variant make for different ranges of weak wallets. This article is _exclusively_ about the two newly discovered variants, and does not cover the Mersenne Twister based vulnerability.
 
@@ -77,7 +77,7 @@ We mapped out the discovered BTC and ETH wallets in a histogram plot to better u
 {% responsive_image_block %}
   figure: true
   path: assets/images/graphs/trustwallet2ab_bip39_128bit_only_histogram_btc_eth_prng_index_2010_2025_graph1.png
-  alt: "Histogram of PRNG creation index for discovered wallets - Trust Wallet IOS<br/>variant A & B - 128 bit wallets<br/>Yearly X-Axis timestamp markers"
+  alt: "Histogram of PRNG creation index for discovered wallets<br/>Trust Wallet iOS variant A & B - 128 bit wallets<br/>Yearly X-Axis timestamp markers"
   target_width: 1100px
 {% endresponsive_image_block %}
 
@@ -87,31 +87,34 @@ We mapped out the discovered BTC and ETH wallets in a histogram plot to better u
 * 2019-01-01: **1,546 x 10⁹** timestamp
 * 2020-01-01: **1,578 x 10⁹** timestamp
 * Total range shown: 2010-01-01 to 2025-01-01
-* Y-Axis capped for readability
+* Y-Axis capped for readability, data is not stacked
 </details><br/>
 
 Two main observations:
 1. The majority of Bitcoin and Ethereum wallets have a PRNG seed that corresponds to wallet creation timestamps from 2018 and 2019.
 2. There is a smaller number of wallets with a more "random" pattern.
 
-Point 1) generally fits to the publicly known timeline of the `Trust Wallet IOS` development and vulnerability (but is not a hard confirmation).
+Point 1) generally fits to the publicly known timeline of the `Trust Wallet iOS` development and vulnerability (but is not a hard confirmation).
 Point 2) indicates that there is some other source of weak wallets in this range that is less time based. Alternatively, it's possible that a subset of app devices had bad clocks for some reasons when creating the wallets.
 
-Since the situation in 2018-2019 is very busy, here is a zoomed in version:
+Since the situation in 2018-2019 is very busy, here is a zoomed-in and annotated version:
 
 {% responsive_image_block %}
   figure: true
   path: assets/images/graphs/trustwallet2ab_bip39_128bit_only_histogram_btc_eth_prng_index_2018_2019_graph2.png
-  alt: "Histogram of PRNG creation index for discovered wallets - Trust Wallet IOS<br/>variant A & B, 2018-05 to 2020-01"
+  alt: "Histogram of PRNG creation index for discovered wallets - Trust Wallet iOS<br/>variant A & B, 2018-05 to 2020-01, data is not stacked"
   target_width: 1100px
 {% endresponsive_image_block %}
 
 A possible interpretation of the graph history:
-* Weak wallets of variant A appear with the first weak software version
-* Weak wallets of variant B appear once a differently vulnerable software version gets released, new wallets of variant A get more rare
-* A patched version get released
-* Historically high BTC prices makes users with existing weak wallets create Bitcoin accounts (?)
-* Some users of both vulnerable software versions keep creating weak wallets months later, likely because did not get the patched app versions yet
+1. Parameter space "before" the vulnerable `Trust Wallet` versions
+2. Weak wallets of variant A appear with the first weak software version
+3. Weak wallets of variant B appear once a differently vulnerable software version gets released
+  * -> New wallets in variant A get more rare
+4. A patched version get released
+  * -> New wallets in variant B get more rare
+5. Historically high BTC prices motivate users to create new wallet mnemonics for Bitcoin accounts (?)
+6. Some users of both vulnerable software versions keep creating weak wallets months later, likely because did not get or install the patched app versions yet
 
 ### Bitcoin On-Chain Movements
 Here is an _initial, incomplete_ analysis of BTC movements to and from weak wallets based on our initial data:
@@ -141,7 +144,7 @@ Note: this describes funds moved over the weak wallets that have been at risk at
 ### Involvement in the 2023-07-12 Theft
 Here are the three biggest outgoing theft transactions from the newly disclosed range of weak wallets on 2023-07-12:
 
-| Transaction | Volume variant A<br/> (`Trust Wallet IOS`) | Volume variant B<br/> (`Trust Wallet IOS`) | Transaction total volume | Date |
+| Transaction | Volume variant A<br/> (`Trust Wallet iOS`) | Volume variant B<br/> (`Trust Wallet iOS`) | Transaction total volume | Date |
 | - | - | - | - |
 | {{ "81cfe97cc16a49398d6986032ec8f6970ea80df5aa0990dcf0164de87136f5bf" | BtcLinkTxUrlSliced }} |		-4,829 BTC | -3,481 BTC |  -9,744 BTC | 2023-07-12 12:41 |
 | {{ "cdd9a2aff7cd0707e31023513cc78aceff7ea7e754e3a9bde9c0482b70a9716c" | BtcLinkTxUrlSliced }} |		-8,161 BTC | none | -8,161 BTC _(incl. fee)_ | 2023-07-12 12:41 |
@@ -158,7 +161,7 @@ At the time of publication, less than $100 USD in total remain on the known BTC
 
 ## Summary & Outlook
 
-In this research update, we've followed up on work by other security researchers who discovered two large new ranges of weak cryptocurrency wallets from (most likely) an older vulnerability in `Trust Wallet` on IOS. We confirmed that these weak wallets exist and that they were involved in the Milk Sad thefts. We also provided new statistics on their distribution and usage.
+In this research update, we've followed up on work by other security researchers who discovered two large new ranges of weak cryptocurrency wallets from (most likely) an older vulnerability in `Trust Wallet` on iOS. We confirmed that these weak wallets exist and that they were involved in the Milk Sad thefts. We also provided new statistics on their distribution and usage.
 
 This is an exciting new piece of the overall Milk Sad puzzle, and we'll likely update this blog post with some new information as it becomes available.