# Tag Info

5

I'll assume the question really is: when I perform low-order-bit steganography on an uncompressed image (inserting 6 bits encoding a character into the low-order bit of 6 bytes coding the R, G and B channels of 2 pixels), I find that compressing the resulting image gives a bigger file than compressing the original image for a given setting of the program ...

4

What you are looking for is a definition of PEM, privacy enhanced mail. Obviously PEM is not just used for mail anymore. The definition of the header lines seems to be best described by section 4.6: "Summary of Encapsulated Header Fields" of RFC 1421: "Privacy Enhancement for Internet Electronic Mail: Part I: Message Encryption and Authentication ...

0

Have a look at order revealing encryption (ORE) schemes: https://eprint.iacr.org/2014/834.pdf

1

You'll have to write the function you are trying to calculate as a polynomial in the two inputs $x$ and $y$. If you are working over the field with $q$ elements as plaintexts, you have to calculate for equality the polynomial $(x-y)^{q-1}$. Greater-than-or-equal (however you define that for finite fields) will be even more complicated.

0

So lets assume a few things: just symmetric primitives suffice; a symmetric key derivation function and single block encrypt with a 64 bit block cipher is sufficiently fast; the ID's are unique and not related to customers; we're not afraid of customers sharing ID's; there is protection against customers simply guessing ID's; Scheme: establish a master ...

0

The pairing description (type, q, h, r, etc.) is the definition of the field that the elliptic curve of some type operates on. The actual curve is identified by its type and is baked into the framework (e.g. PBC) you're using. This definition corresponds to $q$ (group order, same as q), $\mathbb{G}, \mathbb{G}_T$ (groups defined by pairing description and ...

0

The server must give the clients all the necessary information for the clients to be able to compute the pairing. This will differ depending on how pairings are implemented in the system, and what prior knowledge the clients have.

1

Diffie-Hellman relies on a mathematical problem on positive integers. To use it with bytes you just have to convert the bytes to - or use the bytes as - an integer. Usually this would be a unsigned big-endian (or network order) integer. For Diffie-Hellman the parameters consist of the modulus and the base. The public value could be 1024 bits (128 bytes). ...

2

(Q1) Assuming that you talk about the size of the secret key elements which equals the input size of the OWF when you talk about the "input", this should be at least as much as the output size. Consider a function $f: \{0,1\}^m \rightarrow \{0,1\}^n$.The thing to worry about when you choose $m < n$ is a brute force search for a preimage, which in this ...

6

An initialization vector is, in fact, always binary. It's just random bits. So, if you choose to encode those bits as a hexadecimal string for ease of storage or transportation, that is fine. However, since it is the binary that is the IV, you will need to decode it back from hexadecimal to a binary value before using it in the decryption process. As a ...

4

Triple DES is a block cipher. (Specifically, it's a variant of the old DES block cipher with better security, but several times lower performance.) You can use it to encrypt small blocks of data (64 bits = 8 bytes, for Triple DES), but what it's really useful for is as a building block for other cryptographic schemes, such as stream encryption or message ...

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