From 03543e21229e437e03e0f079d53f175f779db316 Mon Sep 17 00:00:00 2001 From: 1HXb9KMAtwNJqz4egi6hJx08EQgJajiBTH <1HXb9KMAtwNJqz4egi6hJx08EQgJajiBTH@bitcoin.cash> Date: Wed, 11 Dec 2019 15:04:31 -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 cc68d15..b9fc275 100644 --- a/protocol/blockchain/hash.md +++ b/protocol/blockchain/hash.md @@ -10,7 +10,7 @@ A variety of hashing algorithms are used throughout the Bitcoin Cash protocol. - A SHA-256 hash is taken of the block header. The output hash is then hashed again with SHA-256. This resultant hash is referred to simply as the block hash and is used as a unique identifier for the block. - 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. - 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 two sets of two identical coinbase transactions, thus repeated hashes. Since 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 the block height is now required to be in the coinbase transaction, 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