Chaffing and Winnowing - How IT Works

How It Works

secure channel insecure channel
Alice Charles Bob
constructs 4 packets, each containing one bit of her message and a valid MAC
Serial Bit MAC
1 1 234
2 0 890
3 0 456
4 1 678
adds 4 chaff packets with inverted bits and invalid MAC, shown in italics (chaffing)
Serial Bit MAC
1 0 321
1 1 234
2 0 890
2 1 987
3 0 456
3 1 543
4 0 765
4 1 678
discards packets with invalid MAC to recover the message (winnowing)

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