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iO from FE for Simple Functions Prabhanjan Ananth Abhishek Jain Amit Sahai
15

iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

Jul 13, 2020

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Page 1: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

iO from FE for Simple Functions

Prabhanjan Ananth Abhishek Jain Amit Sahai

Page 2: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

Our result

FE supporting decryption keys for this functionalityimplies iO for circuits

Page 3: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

(Non-compact FE) implies compact FE

Page 4: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

(Non-compact FE) implies compact FE

Supports multi-keys

Page 5: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

(Non-compact FE) implies compact FE

• This work + [AJ15,BV15]: Non-compact FE implies iO

• Implication: iO based on GGHZ14 mmap assumptions

Page 6: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

(Non-compact FE) implies compact FE

Also observed by Bitansky-Vaikuntanathan’15

• This work + [AJ15,BV15]: Non-compact FE implies iO

• Implication: iO based on GGHZ14 mmap assumptions

Page 7: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

Main Idea

Page 8: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

Non Compact FE

Enc( m ) f

Page 9: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

Non Compact FE

Enc( m ) f

depends on the size of f

Page 10: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

Non Compact FE

Enc( m ) f

Break the functional key into many parts

Page 11: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

Non Compact FE

Enc( m )

1st part of f

nth part of f

.

..

Page 12: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

Non Compact FE

Enc( m )

1st part of f

nth part of f

.

..

ciphertext shrinks

Page 13: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

Resulting scheme: Compact FE !!

Enc( m )

1st part of f

nth part of f

.

..

Page 14: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

• Showed: FE for fsimple implies iO for all functions

Page 15: iO from FEcrypto.2015.rump.cr.yp.to/2a8d73a9a9b067ae3c886a72d05b... · 2015-08-19 · Prabhanjan Ananth Abhishek Jain Amit Sahai. Our result FE supporting decryption keys for this

• link: http://eprint.iacr.org/2015/730.pdf