chaffing and winnowing

[Faustine]

Does anyone know of any serious work being done on developing the concepts of 
winnowing and chaffing, as outlined in Ronald L. Rivest's 1998 
paper 'Confidentiality without Encryption'? (Or any other similar creative uses 
of MACs and authentication keys, for that matter? This line of thought 
certainly seems to have some interesting policy implications, particularly re. 
making the idea of forced key recovery obsolete. Any references to further 
papers or applications would be most welcome...thanks!

~Faustine.

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'We live in a century in which obscurity protects better than the law--and 
reassures more than innocence can.' Antoine Rivarol (1753-1801).