Cryptology ePrint Archive: Report 2020/1019

Security of Streaming Encryption in Google's Tink Library

Viet Tung Hoang and Yaobin Shen

Abstract: We analyze the multi-user security of the streaming encryption in Google's Tink library via an extended version of the framework of nonce-based online authenticated encryption of Hoang et al. (CRYPTO'15) to support random-access decryption. We show that Tink's design choice of using random nonces and a nonce-based key-derivation function indeed improves the concrete security bound. We then give two better alternatives that are more robust against randomness failure. In addition, we show how to efficiently instantiate the key-derivation function via AES, instead of relying on HMAC-SHA256 like the current design in Tink. To accomplish this we give a multi-user analysis of the XOR-of-permutation construction of Bellare, Krovetz, and Rogaway (EUROCRYPT'98).

Category / Keywords: secret-key cryptography / Online AE; streaming encryption; Google's Tink library

Original Publication (with minor differences): ACM CCS 2020

Date: received 23 Aug 2020

Contact author: tvhoang at cs fsu edu

Available format(s): PDF | BibTeX Citation

Version: 20200827:022607 (All versions of this report)

Short URL: ia.cr/2020/1019