10 votes

Why is hybrid encryption more effective than other encryption scheme?

Alice also needs to first decrypt the symmetric key and then decrypt the message. It almost seems like a double work. Encrypting a short plaintext (i.e. the symmetric key) requires only one ...
  • 2,734
7 votes

Make AES more secure by randomising the blocks in an encrypted file

TL,DR: No, don't do it. Use a standard protocol and don't write your own implementation. If you're thinking at the level of AES, CBC and RSA, you're doing it wrong. I recommend crypto_box. I am ...
5 votes
Accepted

How to securely map messages to points on an elliptic curve

If I do have to implement a mapping for security, how would you reccomend I map message values to points, and how should I figure out the maximum message size based on my curve? The default ...
  • 45k
5 votes
Accepted

How to do statistical analysis on encrypted / anonimized data

This type of problem is known as anonymizing data, and it has fairly standard solutions. The obvious way is to use a Format Preserving Encryption method; that is a secret key method that has a fairly ...
  • 136k
5 votes

Why is hybrid encryption more effective than other encryption scheme?

In addition to the other answer. The "Steps of Hybrid Encryption" in the question really are steps of one form of hybrid encryption, built on top of asymmetric encryption. There are other forms of ...
  • 128k
4 votes

Symmetric encryption using RSA for random generated password

The concept of using an asymmetric key (RSA) to encrypt a symmetric key (AES) is not new. This was first popularized by PGP, which is probably what I would encourage you to use to solve your problem. ...
  • 425
4 votes
Accepted

What is this called: encrypt $X$ with key $E$, decrypt $X$ with key $D$?

As correctly pointed out in the comments: The term is asymmetric cryptography, also known as public-key cryptography. How do we know that it's asymmetric encryption? In symmetric encryption the ...
  • 6,346
4 votes
Accepted

Understanding hybrid cryptography's concepts: signing and CA

You're confusing a lot of things: Alice and Bob agrees on a shared private key that is to be used to encrypt You cannot have a "shared private" key; sharing and keeping things private are opposite ...
  • 87.1k
4 votes

Is RSA the only current practical option for asymmetric encipherment of symmetric keys at rest?

As of 2021, is RSA the only practical (i.e. safe, production-ready) option for asymmetric encipherment of symmetric keys at rest? Of course not, there are a number of alternatives. For one, there is ...
  • 136k
4 votes

Why AES code is working even with 3 Rows

Then why is it working, I am not able to understand that. Because the ShiftRows operation in AES leaves the top row unchanged; your code does the same (by ignoring it).
  • 136k
3 votes
Accepted

Is Googles Envelope Encryption the same as Hybrid Encryption?

Hybrid encryption refers to an implementation of a public-key encryption interface by the composition of a public-key primitive to encapsulate a symmetric key that's used with a symmetric algorithm to ...
3 votes

Is Hybrid Encryption CCA secure?

If the KEM is only CPA-secure, then the resulting scheme might not be CCA-secure. For example, consider a CPA-secure KEM that ignores the last bit of its ciphertext. Then it is possible to modify a ...
  • 11.1k
3 votes

Hybrid cryptosystem

In what's described, nothing makes B sure that A sent the message. And that can't be obtained without some secret on A's side. A common solution is to have A sign the (e.g. encrypted) message, and B ...
  • 128k
3 votes
Accepted

Hybrid Symmetric and Asymmetric Encryption

A hybrid cryptosystem consists of both an asymmetric algorithm for key establishment and a symmetric cipher. You are correct in that you establish a symmetric key, and yes, that can be done by ...
  • 87.1k
3 votes
Accepted

When do I need to use hybrid cryptography?

The protocol message size is between 100 bytes to 500 bytes. Do I need to use asymmetric encryption or hybrid cryptography? To support 500 byte messages, you need about your (direct) encryption ...
  • 45k
3 votes
Accepted

Encrypt with elliptic curves

While it is possible to encrypt using elliptic curves, typically some form of hybrid encryption is used (for performance reasons or because the algorithm supports only a few bytes of data). Typically ...
3 votes
Accepted

Doing RSA-KEM with RSA-OAEP

If what you have is a machine that computes RSAES-OAEP and not a machine that computes $x \mapsto x^e \bmod n$, you don't really have the tools to do RSA-KEM. You're better off doing what you were ...
3 votes
Accepted

Is a signature scheme using a hash considered a hybrid cryptosystem?

What I didn't directly see is that a hybrid cryptosystem is not the same thing as hybrid cryptography. A cryptosystem is commonly targeting encryption: it exists of a key generation function $\...
  • 87.1k
3 votes

Using HKDF to derive symmetric keys from a hybrid public-key encryption scheme

Fix an RSA modulus $n$. Here's a way you can send a message $m$ so that only someone who knows the secret factorization of $n$ can read it. Pick an integer $1 < x < n$ uniformly at random. ...
3 votes
Accepted

How can Whatsapp identify forwarded attachments

The attachments are processed as follows (source is the WhatsApp's White Paper); First time of the attachment is sent The sender generates a 32-byte random AES-256 key, $k_1$, and another random 32-...
  • 45.2k
3 votes

Why AES code is working even with 3 Rows

As you might notice, the first row (Index 0) is never called. This makes sense because there is no change in the values contained in the first row by definition. This can be better understood by the ...
  • 1,830
2 votes
Accepted

Using HKDF to derive symmetric keys from a hybrid public-key encryption scheme

Many key exchanges output secrets that are either not uniform or are large but splitting them is unsafe because subsets aren't uniform either. Diffie-Hellman over 4096-bit groups or over 256-bit ...
  • 1,412
2 votes

minimal overhead of ChaCha20 + ECC

32 Bytes (+16 for the tag) Let data be your data, let || denote concatenation and let pkD be ...
  • 45k
2 votes

In cryptography is there such as thing as disguising unencrypted text?

... any item of information may consist of a sequence of bytes which is completely indistinguishable, and I mean completely indistinguishable, from randomly generated sequences How can a would-be ...
  • 19.3k
2 votes
Accepted

Commitment scheme: hiding property

I hope this is not homework. It should be almost the same as proving $H_1=_cH_2$. Just let the distinguisher (that distinguishes $Com_1(m)$ and $R_1$) generate and append $Com_2(m)$ in both worlds. ...
  • 2,645
2 votes

Can I replace DH by a post-quantum key exchange in IBAKE for post-quantum identity-based authenticated key exchange?

The security proof for the original IBAKE protocol is found in IBAKE: Identity-Based Authenticated Key Exchange Protocol. The IBAKE scheme described there uses an Identity Based Key Exchange to ...
2 votes

Is hybrid encryption required to use Attribute based Encryption to encrypt messages?

No, this is not required by Attribute Based Encryption (ABE) itself. However it is a common practice to use so-called "hybrid encryption" when you want to encrypt data using public-key encryption, ...
  • 7,389
2 votes

Using xor encryption in the following use case

It sounds like you're looking to implement something very similar to what was asked about here, with the addition of a signature of the ephemeral public key. But as poncho's answer points out, the ...
2 votes

What's bad about idea of public-key/one-time-pad hybrid cryptosystem?

A one time pad's information-theoretic security comes from several facts about the key. The key is as large as the messsage The key is truly random The attacker has no information about the key. ...
  • 1,564
1 vote
Accepted

Securely "forwarding" a Large message in a hybrid encryption system without sending the actual message

One common way is securely sending the encryption key for each user with their public key and store the encrypted data on somewhere where each user can access. You can do this with RSA-KEM with ...
  • 45.2k

Only top scored, non community-wiki answers of a minimum length are eligible