Linked Questions

0 votes
1 answer
1k views

What is the advantage of Encrypt-then-MAC over Encrypt & MAC separately the plaintext [duplicate]

For secrecy, authentication & integrity, you can either use CipherText = Encrypt(PlainText) Signature = Hash(PlainText) CipherText = Encrypt(PlainText) Signature = Hash(CipherText) Either ...
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  • 1,637
4 votes
2 answers
1k 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 ...
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  • 43
0 votes
0 answers
83 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 ...
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  • 271
136 votes
6 answers
97k views

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

Frequently, we want to send messages that are (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 ...
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  • 5,248
66 votes
3 answers
102k 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?
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  • 786
72 votes
3 answers
22k 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 ...
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  • 44.6k
19 votes
4 answers
9k 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 ...
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  • 5,872
11 votes
9 answers
705 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 ...
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10 votes
5 answers
7k 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 ...
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  • 357
6 votes
1 answer
40k 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 ...
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  • 243
20 votes
1 answer
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 ...
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  • 765
3 votes
3 answers
9k 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 ...
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9 votes
2 answers
2k views

Does secure hashing imply secure symmetric encryption?

I was wondering if the mere existence of a (by some definition) secure cryptographic hash function immediately implies an equally secure symmetric encryption scheme. By my understanding, one could to ...
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6 votes
6 answers
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 ...
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11 votes
2 answers
2k views

Random data CBC padding scheme?

When using AES in CBC mode, padding is required when the last plaintext block has not the length required by the cipher. Let's say $k$ mode bytes would be required to fill the block. My idea was to ...
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