Questions tagged [key-size]
Key size is the size measured in bits of the key used in a cryptographic algorithm.
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Given algorithms A and B with 128bit & 256bit variants, is A128 AND B128 keys better, equal, or less strength than either A256, or B256?
I'm not comparing an algorithm specifically because I'm interested in the generic aspect of key lengths. If I'm wrong to do that then I could bring up particular sponge functions to use. The idea is ...
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Key size of a repeating key XOR-encrypted message using Hamming distance
To find possible key sizes for an encrypted message, I break the message into blocks with length s,
...
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1answer
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Requirements for RSA key parameters
Recently I'm working with a chinese vendor for POS devices and their devices use 2048bit RSA keys for signing binaries. I had to generate a public/private pair (so I can sign my own binaries) and I ...
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Are all sizes of RSA keys possible? [duplicate]
I mistakenly thought that RSA keys could only be powers of two(1024, 2048, 4096 etc.) but a few days ago read about a 1536-bit and 1160-bit RSA key. I am wondering is it possible to have an RSA key of ...
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How many keys in columnar transposition
In a book I am reading it says that the message Common sense is not so common. (which has 30 characters, space and punctuation included) has a range of possible ...
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1answer
38 views
Are short ElGamal keysizes acceptable (1024-bit or lower) in cases where security is only necessary in a short timeframe
I am working on an efficient mental poker framework. I have implemented a functional and secure commutative encryption scheme based on ElGamal as described in:
http://groups.csail.mit.edu/cis/theses/...
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Effect of longer key on DES security
I am reading a book on cryptography and the author states that one of the complaints of the research community was that DES key length was chosen to be too short.
I am trying to depict how DES would ...
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Recommended key size for DKIM
What is the recommended key length for DKIM? I'm currently thinking about a 1024-bit key vs. a 2048-bit one.
From the crypto point of view for RSA, 2048 or 4096 bits is clearly recommended--no ...
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How to encrypt a small number of identities (which are related to each other)? / Which algorithm has the smallest bit-length?
I'm looking for an encryption with as small numbers as possible.
Given a small group of identities ($G$) (e.g. numbers from $1$ to $N$).
Given one entry (or a small number) $e_i$ allows to compute ...
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1answer
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Security of ciphersuite and key
Is anyone able to cite resources that can be based on choosing a cipher suite?
In my case, for a VPN server (OpenVPN) I chose a set of ciphers:
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
It provides 128 ...
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1answer
151 views
Why is the NIST recommendation for the private key exponent so much smaller than the modulus?
NIST recommends a 256-bit private key exponent for DLP with a 3072-bit modulus. This question answered how the modulus was chosen/calculated, however, why isn't the private key size closer to the ...
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When does the SIS (Short Integer Solution) Lattice-problem start becoming easy (According to the parameters size)?
SIS (Short Integer Solution) Problem : Given $m$ uniformly random vectors $a \in Z_q^n$, grouped as the columns of a matrix $A \in Z_q^{n.m}$, find a nonzero integer vector $z \in Z^m$ with $||z|| \...
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How is the recommended NIST modulus for DLP chosen/calculated?
NIST recommends a 256-bit private key exponent for DLP with a 3072-bit modulus. From this answer it appears that the range of private key numbers is derived by calculating a prime modulus via $2⋅p$ ...
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Can I use XOR to establish a longer shared secret?
SIKEp434 can only be used to encapsulate a 16 byte (128 bit) shared secret key. Most encryption algorithms these days (specifically (X)ChaCha20) require a 256 bit key to be secure, especially in a ...
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1answer
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Maximum security strength in bits of ISAAC cipher?
Wikipedia claims key length can be very big in this cipher, so I assume it can offer a million bits of security provided entropy of key is the same?
Of course I can SHA-256 hash the key to allow any ...
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Minimal secure index of quasi-cyclic codes for code-based cryptography
It is well-known that keys (generator matrices) of code-based cryptography are very large for its practical usage. To reduce them scientists propose to use families of quasi-cyclic codes. I remind ...
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Security strength of JPBC Type A curve compared to SecP curve
I recently encountered some problems when learning about the JPBC library.
Does the curve generated by (J)PBC using the method typeAcurvegenerator(160,512) and the ...
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1answer
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I need help determining the best encryption options based on System.Security.Cryptography in .NET
I asked a question here, and received a great summary but was redirected here. Covering the answers of the post, it was noted and suggested that:
Use of plain (CBC) mode. They suggested to use GCM ...
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1answer
702 views
Length of password requirement using openssl aes-256-cbc
I am using the following OpenSSL command to AES 256 encrypt a file:
...
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1answer
118 views
Guessing the key in AES256-GCM? [duplicate]
I assume that my case is weird but I've the following information:
IV: 0x263e or 0x3e26
Auth tag: 0x25
AES256-GCM encrypted payload: 0x4eec96df534ade4c013a
AES256-GCM decrypted payload: ...
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1answer
664 views
How many bytes of data does AES 256 encrypt at one time?
Since the block size of AES 256 is 256, how would we calculate the bytes of data AES 256 encrypts at one time?
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80-bit collision resistance because of 80-bit x87 registers?
This is just a curious question, and it probably doesn't belong here anyway, and I'm just being bold asking it here.
80-bit used to be considered an adequate level of security, Skipjack and SHA1 ...
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1answer
389 views
Extracting Zip using Only the AES Key
I have set myself a little challenge, to see if I can decrypt my own text file from with a ZIP file...
The AES Key from my encrypted ZIP is all I have managed to extract,
how do I decrypt the ...
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2answers
176 views
Is it required to use a random IV for AES-CBC with random key per message? [duplicate]
I'm developing a program to encrypt and decrypt a file with AES-256/CBC in Java. And I want it to be safe enough. In my case, I generated random AES key for each file to encrypt and decrypt them.
My ...
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Why does Laravel only support AES-256-CBC?
Modern Laravel uses OpenSSL to provide AES-256-CBC encryption along with a MAC. However, I was under the impression that this is not a particularly secure approach.
Why does Laravel only support AES-...
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How secure is a 4 digit seed?
When I Use a 4 digit random number(e.g. 4468) as seed for a (manual) Stream cipher and straddle it to the length of the plaintext using a lagged fibonnacci generator, can this seed be found by brute ...
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1answer
176 views
AES-256-CBC with random IV - storing same plaintext as same ciphertext
I am encrypting some information stored in a column of a MySQL database.
The column can contain repeated values, let's say the table has 7 rows and the column to be encrypted has the following values:...
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1answer
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cryptographic accumulators: accumulator size vs. max. number of set members?
Here's a basic question about cryptographic accumulators, or at least ones based on fixed-size accumulator values (such as RSA ones based on modulo arithmetic), that is strangely not even mentioned in ...
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1answer
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How Secure is gpg Command Using Symmetric AES-256 From Being Cracked
How secure is any data encrypted using the following command:
gpg -o *encrypted_output_file_name* --symmetric --cipher-algo AES256 *file_to_be_encrypted*
Can ...
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1answer
87 views
Key, plaintext block and ciphertext block permutations question
Question: If a cipher’s key size is $k$ bits and its block size is $b$ bits, how many possible keys are there, how many possible plaintext blocks are there, and how many possible ciphertext blocks are ...
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Why is Diffie-Hellman Insecure If Order of the Generator Has Only Small Prime Factors?
In this post from security SE, Tom Leek mentioned that, for Diffie-Hellman to be secure order of the group $g$ should have a prime factor at least $2k$ bits long, where $k$ is the security parameter.
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How many bits should I request from PBKDF2 to create a strong password?
I'm building a tool which generates passwords by hashing a service name with a master key. PBKDF2 was primarily chosen due to availability in the Web Crypto API.
What would be a secure value for the ...
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1answer
2k views
What is the recommended minimum key length for ECDSA signature
I want to identify the proportion of certificates that use unrecommend ECDSA key length for TLS certificates based on some data I collected.
By looking at a standard like NIST for example, I find ...
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3answers
241 views
What is the largest key size that could be carried by a shuffled deck of playing cards?
If you are carrying a standard 52 card pack of cards (no jokers) what is the largest key size, or the amount of data the cards can hold?
Without the cards being marked or distinguishable from an ...
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1answer
153 views
Is this device authentication method (using AES-256) secure?
Let's say we have:
client_id_ran: 256 bit random text (chosen only once for whole system) used to generate client_id by ...
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1answer
258 views
What are the disadvantages of XOR key derivation?
Assume a 256-bit Key and a 256-bit Salt, with uniformly distributed entropy, both fully independent.
Assume ...
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2answers
884 views
How to encrypt file with RSA and AES that anyone with RSA key can decrypt them?
How to encrypt a file with RSA and AES-256 that anyone with RSA key can decrypt them?.
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1answer
552 views
Does password length affect AES encrypt/decrypt velocity?
I'm implementing crypto in Node, following this article: https://lollyrock.com/articles/nodejs-encryption/
It defines:
...
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Encrypt multiple files with OpenSSL securely [closed]
I wish to encrypt potentially gigabytes of data on my pc, and I wish to be able to decrypt and use those files.
However, I am a noob, so bear with me.
My idea is to use ...
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1answer
338 views
Differences between Webcrypto (js) and Cryptodome.Cipher.AES (python) [closed]
I'm trying to understand the difference in output of AES decrypt (GCM mode) using Webcrypto and Cryptodome.Cipher.AES in python.
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1answer
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Why can't decrypt with OpenSSL if salt changed (for CBC and ECB)
A file encrypted with OpenSSL (with, for example, AES 256-bit mode CBC) using the Linux command
openssl enc -aes-256-cbc -in texte -out encrypted_texte -k password
...
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2answers
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Can one trade off the number of iterations for key length with the PBKDF2?
When using the PBKDF2, is one taking on significant risk if one chooses to lower the number of iterations and choose to have very long keys?
Can I XOR my message with a a very long key (plain-text ...
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2answers
61 views
Maximum number of possible keys for a fixed-length password?
I'm reviewing some information and possibilities regarding key space size following a unique password requirement, as it were.
This particular requirement is a fixed-length password of 12 characters, ...
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1answer
2k views
Encryption / Decryption using AES-256 GCM
I am new in cryptography and I am facing some complications in encryption-decryption. I am trying to use AES-GCM with a 256-bit AES key and a 96-bit nonce. I use an open source project (Vault) to ...
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2answers
567 views
Why would Diffie-Hellman Group 21 be 521 bits rather than 512?
Diffie-Hellman groups tend to increment in key sizes as you'd expect up until group 21. Any idea why the key size is 521 rather than 512? I haven't been able to find an answer at all.
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1answer
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X25519 - why openssl shows 253 bits?
When using ECDHE with Curve25519 with openssl:
Server Temp Key: X25519, 253 bits
I thought when we use X25519, it use 256 bit key. Why openssl shows the server temp key as 253 bits?
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2answers
971 views
How much time does AES decryption take?
I am attempting to decrypt a 90 GB file that is encrypted using AES-256. I have the password. How long should this take to complete? I've had the process running for over 3 days with no progress.
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1answer
316 views
Is it possible to reverse Ansible vault data?
I would like to publish on github a full set of ansible playbooks.
Some files contains sensitive data, so I have 'vaulted' them, encrypted.
You can find the format description here and some relevant ...
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1answer
176 views
Is it possible to successfully encrypt/decrypt in DUKPT using different sized BDKs?
We are having our P2PE Solution validated against the PCI P2PE standard. We currently use a TDEA 2-key based BDK, and IPEK in both the encryption and decryption environments. ANSI X9.24-1 (2009) ...
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What is the minimum and maximum value of an RSA private exponent?
Is it possible to calculate the minimum and maximum value of the private exponent for an RSA key, for example for a 1024 key size? In other words, what is the range of values in which the private ...
