4 ms·

My interpretation as someone who is not an expert on cryptography: The final cyphertext of an encryption system should be indistinguishable from noise - the le

My interpretation as someone who is not an expert on cryptography: The final cyphertext of an encryption system should be indistinguishable from noise - the less random the output looks, the more information an attacker gains. The output of your 512-bit encryption should therefore look like noise already. Converting noise to noise should therefore result, predictably, in more noise. So I'm going to say "no, you can't tell".

dogma1138 5y ago
In theory yes in practice crypto systems add additional data to assist in decryption and interoperability. Key size, algo, even key identifier are often added as meta data. And that is before you get into less than perfect encryption.
pc86 5y ago
Cryptography is specialized (and counterintuitive) enough that perhaps we should just let people who know what they're talking about respond rather than repeating or just making up what "feels right" to our lay interpretations of incredibly complex topics.
- Jerrrry 5y ago
  I know what I am talking about: above poster is correct. Proper encryption, maximum compression, and random bytes are all indistinguishable, as they have maximum entropy. I only failed 9th grade three times, so feel free to correct me.
  - TomSwirly 5y ago
    > are all indistinguishable, without additional information! I can prove to you that you're seeing an encrypted message by giving you the decryption key, and I can prove to you that you're seeing compression by giving you the decompression algorithm. However, there is no way to prove that random bytes are _really_ random.
    - Jerrrry 5y ago
      >However, there is no way to prove that random bytes are _really_ random. well of course, because the opposite is true, any string of bytes can by XOR'd to something meaningful. https://en.wikipedia.org/wiki/One-time_pad https://en.wikipedia.org/wiki/One-time_pad
  - inkeddeveloper 5y ago
    It’s a tough grade.
- batch12 5y ago
  What we have been taught or what we understand about cryptography is just as important to discuss. What you said sounds a bit like "let the adults talk" and is condescending.
- NavinF 5y ago
  “20 years of abstinence-only cryptography education hasn’t gotten us anything but an endless supply of bad crypto in production systems”
gizmo686 5y ago
Unless your "ciphertext" includes a header saying "this data in encrypted with 512-bit AES-cbc" Instead of auditing the code/file format, it may be less error prone to just re-encrypt the entire file thereby hiding any metadata that the encryption program attaches.

dogma1138 5y ago

In theory yes in practice crypto systems add additional data to assist in decryption and interoperability. Key size, algo, even key identifier are often added as meta data. And that is before you get into less than perfect encryption.

pc86 5y ago

Cryptography is specialized (and counterintuitive) enough that perhaps we should just let people who know what they're talking about respond rather than repeating or just making up what "feels right" to our lay interpretations of incredibly complex topics.

Jerrrry 5y ago
I know what I am talking about: above poster is correct. Proper encryption, maximum compression, and random bytes are all indistinguishable, as they have maximum entropy. I only failed 9th grade three times, so feel free to correct me.
- TomSwirly 5y ago
  > are all indistinguishable, without additional information! I can prove to you that you're seeing an encrypted message by giving you the decryption key, and I can prove to you that you're seeing compression by giving you the decompression algorithm. However, there is no way to prove that random bytes are _really_ random.
  - Jerrrry 5y ago
    >However, there is no way to prove that random bytes are _really_ random. well of course, because the opposite is true, any string of bytes can by XOR'd to something meaningful. https://en.wikipedia.org/wiki/One-time_pad https://en.wikipedia.org/wiki/One-time_pad
- inkeddeveloper 5y ago
  It’s a tough grade.
batch12 5y ago
What we have been taught or what we understand about cryptography is just as important to discuss. What you said sounds a bit like "let the adults talk" and is condescending.
NavinF 5y ago
“20 years of abstinence-only cryptography education hasn’t gotten us anything but an endless supply of bad crypto in production systems”

gizmo686 5y ago

Unless your "ciphertext" includes a header saying "this data in encrypted with 512-bit AES-cbc" Instead of auditing the code/file format, it may be less error prone to just re-encrypt the entire file thereby hiding any metadata that the encryption program attaches.