-Each of the two Checksum Tags is constructed over separate Reed-Solomon messages of length 32. The Even Message Tag contains characters from even-indexed positions (0, 2, ..., 30) of the Padded Namespace Tag and Payload String, and the Odd Message Tag contains characters from odd-indexed positions (1, 3, ..., 31), as specified in Section 5.6. Consecutive characters in the Namespace String or the Payload String therefore alternate between the two independent Reed-Solomon messages. The Interleaved Checksum similarly alternates its characters between the two Reed-Solomon codewords. A burst of up to 8 consecutive substitution errors confined to the Namespace String, to the Payload String, to the Interleaved Checksum, or spanning the boundary between the Payload String and the Interleaved Checksum, is guaranteed to be detected, because at most 4 errors will be distributed to each codeword. More generally, any error pattern that produces at most 4 symbol errors in each Reed-Solomon codeword is guaranteed to be detected by the checksums. Errors affecting the Prefix, Pads, or the length of any component are always detected by the validation algorithm independently of the checksums.
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