ViaBTC, Foundry USA, and F2Pool blocked transactions involving addresses from the OFAC SDN list.
Filtering transactions by one pool as a whole does not affect the network's resistance to censorship, but the situation requires further monitoring.
Mining pools started rejecting transactions from addresses or to addresses in the OFAC SDN list, without adding them to blocks. A similar situation was noticed by a bitcoin developer under the pseudonym 0xB10C.
From September to October 2023, the expert recorded six similar cases using a special service. One from ViaBTC, another from the Foundry USA pool, and four more from F2Pool.
Subsequent detailed analysis showed that filtering by the first two miners was false due to the specifics of the software. However, in the situation with F2Pool, the blocking was intentional. 0xB10C reminded that the latter belongs to the Chinese.
Each block is missing one "sub-sanctioned" transaction. It combines 150 inputs with 2 out of 3 multi-signatures. They typically spend funds received from 3PKiHs4GY4rFg8dpppNVPXGPqMX6K2cBML.
OFAC added this address to the SDN list on April 14, 2023.
According to 0xB10C, due to the use of multi-signatures in most of the 150 inputs ,a" missed " transaction weighs an impressive 43,842 bytes. The initiator provided the miner with a sufficient fee to enable it, the specialist stressed.
Before creating block 810727 ..ccda1498, the transaction was in the analyst's mempool for about four hours, but instead F2Pool added another one (in the illustration below — at the bottom right). It also consolidates 150 entries, but does not spend funds from the sanctioned address.
It charges the same fee of 446,260 sat, but it is 3 bytes more than 11 at 44,020 bytes. This means that the missing transaction c6a66836. has a slightly higher coefficient than 907e1f45…
"When strictly sorted by coefficient, the pool should have included the missing transaction. In practice, it is unlikely that 3 MB of additional space will affect the total amount of fees, " the expert said.
F2Pool did not include a similar transaction with a" weight " of 170 kWU and in block 811,791 ..af4453d6. Similar to the previous consolidation operations, the size of this one was 42,459 bytes with a commission of 446,260 sat based on 10.5 sat/byte. According to the service's calculations, it took four minutes from the moment of getting into the analytics mempool to block mining.
There was enough free space in 811,791, 2.86 MWU out of 4 MWU transactions were paid less than the mentioned 10.5 sat/byte. In mempool. space, this operation involving 3PKiHs4GY4rFg8dpppNVPXGPqMX6K2cBML was marked as "deleted".
In block 811920 ..00badf62 a similar situation was repeated. A transaction with a "weight" of 170 kWU was skipped if there was enough space in the block and an acceptable commission (1.44 MWU out of 4 MWU were lower based on sat per byte).
According to the analyst, with a high probability, F2Pool should have "seen" it, since it stayed in the mempool of its node for two minutes.
To the last detected block 813357 ..63ac1669 the operation was not enabled after more than 25 minutes of waiting.
"Due to such a long time, it is unlikely that the transaction has not yet spread to one of the F2Pool nodes," the specialist stressed.
As in previous cases with a "weight" of 172 kWU, it met the criteria for inclusion (0.684 MWU out of 4 MWU were lower based on sat per byte), he said.
The expert found it difficult to answer the question whether F2Pool filters out only 3PKiHs4GY4rFg8dpppNVPXGPqMX6K2cBML or all addresses from the OFAC SDN list.
In conclusion, 0xB10C noted that filtering transactions by a single pool does not affect the network's overall resistance to censorship.
"Further monitoring will allow us to determine whether other players will resort to this practice. This will also provide an opportunity [ ... ] to make an informed decision about switching to competitors in case of disagreement with such a policy," the specialist said.
Recall that in November, OFAC imposed sanctions against Russian citizen Ekaterina Zhdanova. According to the authorities, she helped representatives of the Russian elite circumvent international restrictions with the help of cryptocurrencies.
Filtering transactions by one pool as a whole does not affect the network's resistance to censorship, but the situation requires further monitoring.
Mining pools started rejecting transactions from addresses or to addresses in the OFAC SDN list, without adding them to blocks. A similar situation was noticed by a bitcoin developer under the pseudonym 0xB10C.
From September to October 2023, the expert recorded six similar cases using a special service. One from ViaBTC, another from the Foundry USA pool, and four more from F2Pool.
Subsequent detailed analysis showed that filtering by the first two miners was false due to the specifics of the software. However, in the situation with F2Pool, the blocking was intentional. 0xB10C reminded that the latter belongs to the Chinese.
Each block is missing one "sub-sanctioned" transaction. It combines 150 inputs with 2 out of 3 multi-signatures. They typically spend funds received from 3PKiHs4GY4rFg8dpppNVPXGPqMX6K2cBML.
OFAC added this address to the SDN list on April 14, 2023.
According to 0xB10C, due to the use of multi-signatures in most of the 150 inputs ,a" missed " transaction weighs an impressive 43,842 bytes. The initiator provided the miner with a sufficient fee to enable it, the specialist stressed.
Before creating block 810727 ..ccda1498, the transaction was in the analyst's mempool for about four hours, but instead F2Pool added another one (in the illustration below — at the bottom right). It also consolidates 150 entries, but does not spend funds from the sanctioned address.
It charges the same fee of 446,260 sat, but it is 3 bytes more than 11 at 44,020 bytes. This means that the missing transaction c6a66836. has a slightly higher coefficient than 907e1f45…
"When strictly sorted by coefficient, the pool should have included the missing transaction. In practice, it is unlikely that 3 MB of additional space will affect the total amount of fees, " the expert said.
F2Pool did not include a similar transaction with a" weight " of 170 kWU and in block 811,791 ..af4453d6. Similar to the previous consolidation operations, the size of this one was 42,459 bytes with a commission of 446,260 sat based on 10.5 sat/byte. According to the service's calculations, it took four minutes from the moment of getting into the analytics mempool to block mining.
There was enough free space in 811,791, 2.86 MWU out of 4 MWU transactions were paid less than the mentioned 10.5 sat/byte. In mempool. space, this operation involving 3PKiHs4GY4rFg8dpppNVPXGPqMX6K2cBML was marked as "deleted".
In block 811920 ..00badf62 a similar situation was repeated. A transaction with a "weight" of 170 kWU was skipped if there was enough space in the block and an acceptable commission (1.44 MWU out of 4 MWU were lower based on sat per byte).
According to the analyst, with a high probability, F2Pool should have "seen" it, since it stayed in the mempool of its node for two minutes.
To the last detected block 813357 ..63ac1669 the operation was not enabled after more than 25 minutes of waiting.
"Due to such a long time, it is unlikely that the transaction has not yet spread to one of the F2Pool nodes," the specialist stressed.
As in previous cases with a "weight" of 172 kWU, it met the criteria for inclusion (0.684 MWU out of 4 MWU were lower based on sat per byte), he said.
The expert found it difficult to answer the question whether F2Pool filters out only 3PKiHs4GY4rFg8dpppNVPXGPqMX6K2cBML or all addresses from the OFAC SDN list.
In conclusion, 0xB10C noted that filtering transactions by a single pool does not affect the network's overall resistance to censorship.
"Further monitoring will allow us to determine whether other players will resort to this practice. This will also provide an opportunity [ ... ] to make an informed decision about switching to competitors in case of disagreement with such a policy," the specialist said.
Recall that in November, OFAC imposed sanctions against Russian citizen Ekaterina Zhdanova. According to the authorities, she helped representatives of the Russian elite circumvent international restrictions with the help of cryptocurrencies.
