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Internals.md
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@ -42,9 +42,11 @@ If correct order is not required, Picocrypt will take the SHA3-256 of each keyfi
If correct order is required, Picocrypt will concatenate the keyfiles together in the order they were dropped into the window and take the SHA3-256 of the combined keyfiles. If the order is not correct, the keyfiles, when appended to each other, will result in a different file, and thus a different hash. So, the correct order of keyfiles is required to decrypt the volume successfully.
# Reed-Solomon
By default, all Picocrypt volume headers are encoded with Reed-Solomon to improve resiliency against bit rot. The header uses N+2N encoding, where N is the size of a particular header field such as the version number, and 2N is the number of parity bytes. If Reed-Solomon is to be used with the input data itself, the data will be encoded using 128+8 encoding, with the data being read in chunks of 1 MiB, and the final set padded to 128 bytes using PKCS#7.
By default, all Picocrypt volume headers are encoded with Reed-Solomon to improve resiliency against bit rot. The header uses N+2N encoding, where N is the size of a particular header field such as the version number, and 2N is the number of parity bytes added. Using the Berlekamp-Welch algorithm, Picocrypt is able to automatically detect and correct up to 2N/2=N broken bytes.
In the edge case where the final 128-byte block happens to be padded so that it completes a full 1 MiB chunk, a flag is used to distinguish whether the last 128-byte block was padded originally or if it is just a full 128 bytes of data.
If Reed-Solomon is to be used with the input data itself, the data will be encoded using 128+8 encoding, with the data being read in 1 MiB chunks and encoded in 128-byte blocks, and the final block padded to 128 bytes using PKCS#7.
To address the edge case where the final 128-byte block happens to be padded so that it completes a full 1 MiB chunk, a flag is used to distinguish whether the last 128-byte block was padded originally or if it is just a full 128-byte block of data.
# Just Read the Code
Picocrypt is a very simple tool and only has one source file. The source Go file is less than 2k lines and a lot of the code is dealing with the UI. The core cryptography code is only about 1k lines of code, and even so, a lot of that code deals with the UI and features of Picocrypt. So if you need more information about how Picocrypt works, just read the code. It's not long, and it is well commented and will explain what happens under the hood better than a document can.
Picocrypt is a very simple tool and only has one source file. The source Go file is less than 2k lines and a lot of the code is dealing with the UI. The core cryptography code is only about 1k lines of code, and even so, a lot of that code deals with the UI and other features of Picocrypt. So if you need more information about how Picocrypt works, just read the code. It's not long, and it is well commented and will explain what happens under the hood better than a document can.