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Why does a transaction have the fields attachmentTimestampLowerBound and attachmentTimestampUpperBound. What does it mean for a timestamp to have bounds?

blockmined
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shoe
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You have no way of knowing when exactly a transaction was attached to the tangle (because you can even set this value), instead you can have a max interval you can trust, maybe giving a example you be easier to understand.

I am at home with my family, I decide to go the store to buy some icecream, so I leave my house at 9:00 AM and they see it. I buy the Icecream at 10:00 AM and arrive at home at 11:00 AM. I say to them I bought the icecream at 9:30 AM, is that true? No, but they can know the possible time interval I bought it. The 9:30 AM is the timestamp they see, 9:00 AM is the attachmentTimestampLowerBound and 10:00 AM is the attachmentTimestampUpperBound.

  • If I can set attachmentTimestamp can I not also set either of the bounds, making it seem like whatever interval I want is valid? – shoe Mar 02 '18 at 19:57
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    One can determine the confidence intervals for timestamps with reasonable accuracy using algorithms, a malicious node could set the timestamp but not the bounds. You can see the math at On the timestamps in the tangle –  Mar 02 '18 at 20:18