From 6fd4c6378adfed4d6d30c68fca92c76b89e1e93a Mon Sep 17 00:00:00 2001 From: 1HXb9KMAtwNJqz4egi6hJx08EQgJajiBTH <1HXb9KMAtwNJqz4egi6hJx08EQgJajiBTH@bitcoin.cash> Date: Wed, 11 Dec 2019 15:29:05 -0500 Subject: [PATCH] wiki commit --- protocol/blockchain/hash.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/protocol/blockchain/hash.md b/protocol/blockchain/hash.md index 727ddbe..bbb18f0 100644 --- a/protocol/blockchain/hash.md +++ b/protocol/blockchain/hash.md @@ -11,7 +11,7 @@ A variety of hashing algorithms are used throughout the Bitcoin Cash protocol. - This double hash removes the possibility of a [length extension attack](https://en.wikipedia.org/wiki/Length_extension_attack) which a single SHA-256 is vulnerable to. While this is generally not a problem for Bitcoin Cash since the pre-image (the actual data of the block) is available, it trades a minor amount of inefficiency for confidence that this property of SHA-256 cannot be exploited. - Double SHA-256 has it's own operation for ease-of-use, [OP_HASH256](/protocol/blockchain/script/opcodes/op-hash256) - Transaction Hashing - - Transactions are hashed using a single application of SHA-256. This is referred to as the transaction hash and is used to uniquely identify the transaction. (NOTE: Historical transaction hashes are not universally unique, there are two sets of two identical coinbase transactions and thus repeated hashes. Since [BIP-34](/protocol/forks/bip-0034), the block height is now required to be in the coinbase transaction, this should not be possible in the future.) + - Transactions are hashed using a single application of SHA-256. This is referred to as the transaction hash and is used to uniquely identify the transaction. (NOTE: Historical transaction hashes are not universally unique, there are two sets of two identical coinbase transactions and thus repeated hashes. Since [BIP-34](/protocol/forks/bip-0034), the block height is now required to be in the coinbase transaction, so this should not be possible in the future.) - The two cases where this occurred are the following transactions which each appear in two blocks: - D5D27987D2A3DFC724E359870C6644B40E497BDC0589A033220FE15429D88599 - E3BF3D07D4B0375638D5F1DB5255FE07BA2C4CB067CD81B84EE974B6585FB468