Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 2FE: Two-Factor Encryption for Cloud Storage   Encrypted cloud storage services are steadily increasing in popularity, with
many commercial solutions currently available. In such solutions, the cloud
storage is trusted for data availability, but not for confidentiality.
Additionally, the user's device is considered secure, and the user is expected
to behave correctly.
  We argue that such assumptions are not met in reality: e.g., users routinely
forget passwords and fail to make backups, and users' devices get stolen or
become infected with malware. Therefore, we consider a more extensive threat
model, where users' devices are susceptible to attacks and common human errors
are possible. Given this model, we analyze 10 popular commercial services and
show that none of them provides good confidentiality and data availability.
  Motivated by the lack of adequate solutions in the market, we design a novel
scheme called Two-Factor Encryption (2FE) that draws inspiration from
two-factor authentication and turns file encryption and decryption into an
interactive process where two user devices, like a laptop and a smartphone,
must interact. 2FE provides strong confidentiality and availability guarantees,
as it withstands compromised cloud storage, one stolen or compromised user
device at a time, and various human errors. 2FE achieves this by leveraging
secret sharing with additional techniques such as oblivious pseudorandom
functions and zero-knowledge proofs. We evaluate 2FE experimentally and show
that its performance overhead is small. Finally, we explain how our approach
can be adapted to other related use cases such as cryptocurrency wallets.

28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
16
The categories of this paper are: stat
4
The categories of this paper are: cond-mat
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg