Linked Questions

1
vote
2answers
363 views

HMAC does it matter if I chose the cipher text or the plain text as the message? [duplicate]

I am using HMAC to create a message authentication code. My question is, does it matter if I use cipher text + encryption key or ...
0
votes
0answers
50 views

Encrypted vs unencrypted digital signatures [duplicate]

Is there a difference in terms of security between An encrypted stream of bits obtained by encrypting a plaintext concatenated with it's signature $ C = E_k(plaintext||\sigma)$ where $E$ is a ...
0
votes
0answers
23 views

Should i hash or encrpt the data first? Why? [duplicate]

Lets say alice is trying to send data to bob , should alice first hash the data and then encrpt or vice versa
-1
votes
0answers
14 views

Sign and encrypt or just sign? [duplicate]

When signing a file or message we can encrypt it with our private key. Is there really any good reason to do this (other than preventing the lazy from reading our message in transit)? Since this ...
109
votes
5answers
67k views

Should we sign-then-encrypt, or encrypt-then-sign?

We often want to send messages that are both (a) encrypted, so passive attackers can't discover the plaintext of the message, and (b) signed with a private-key digital signature, so active attackers ...
51
votes
3answers
64k views

Why shouldn't I use ECB encryption?

I'm using Java to generate encrypted strings, and I get this warning at build time: ECB encryption mode should not be used So I'm wondering why I shouldn't use ECB and what I can use instead?
52
votes
3answers
12k views

Signal vs Telegram in terms of protocols?

Some time ago, the question was asked in chat, why MTProto (Telegram's protocol) is supposedly worse than Axolotl (Signal's protocol) as both protocols have been the inventions of their respective ...
17
votes
4answers
6k views

Why is OCB-AES mode not becoming a standard for authenticated encryption?

The OCB mode of authenticated encryption (used for example with AES) is the fastest way to provide authenticity and confidentiality without having to strive into questions like: Encrypt then MAC, MAC ...
11
votes
9answers
645 views

Physical analogue for MACs

What would be a good analogue with which to describe Message Authentication Codes to a person who has little to no understanding of cryptography? For instance, a vault is a reasonable analogue for ...
10
votes
5answers
6k views

Tamper-proofing log files

Problem Overview I want to securely store log files so the contents are secret, and they can't be modified without detection. The files will be encrypted using authenticated encryption (AES in GCM ...
3
votes
3answers
8k views

How to use HMAC-SHA1, HMAC-SHA2 in conjunction with AES

I understand how to compute HMAC-SHA1, HMAC-SHA2 etcetera. Please explain why/how is the resulting HMAC value is used in conjunction with AES for encryption/decryption and signing/verifying. In ...
6
votes
6answers
2k views

Is there an authenticated encryption scheme where the recipient can attribute the message to a single sender?

With a standard authenticated encryption scheme (or MAC), Alice and Bob share a symmetric key. When Alice sends something to Bob, Bob can check that it is authentic. At that point, Bob can deduce ...
3
votes
1answer
18k views

Why is padding used in CBC mode?

I am newbie to CBC crypto: When I try decrypt the cipher text to recover the plain text, things are not going smoothly as I face some issues in the decryption process with padding and not obtaining ...
17
votes
1answer
2k views

Why choose an authenticated encryption mode instead of a separate MAC?

What are cryptographic reasons to choose an authenticated-encryption mode of operation (such as GCM) over a traditional encryption mode plus an independent MAC, or vice versa? Assume there is no ...
7
votes
1answer
1k views

Is Encrypt(m||k2, k1) secure authenticated encryption?

I don't fully understand the need for MAC algorithms to authenticate encrypted messages. As I understand, the standard is to send something like $\mathrm{E}(m,k) \| \mathrm{MAC}(m,k)$ where $E$ is an ...

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