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Mar
25
comment Authentication using a one-time pad
Have you modeled the value this system is protecting? $2^{32}$ sounds like it would be very simple to brute force attack it. All an attacker needs to do is forge a key offset of 0 for each message, and he has the winning hand. I like @poncho's suggestion of using a minimal-memory strong cypher as both the encryption and hash mechanisms, which gets further away from the roll-your-own nature of the OTP suggestion.
Mar
24
comment Authentication using a one-time pad
Not hare-brained, but you need enough bits in each of message to defend against corrupted or tampered messages, which takes a lot more than 4 bits. You also need to consider how these machines will securely re-sync if a message is lost. Restarting a one-time pad would make it be more than one-time!
Mar
24
comment credit card number encryption using aes-ctr mode
it's been a few years since I've seen them, but they were issued by American banks. I was,also basing my statement on your wording choice of "characters", not digits. 16 characters is 128 bits (ASCII), but you can obviously encode many more digits if you are willing to encode it as a big integer or BCD value. That conversion also risks loss of fidelity in the case where an issuer encodes any other value, such as a driver's license or proprietary gift card.
Mar
24
comment credit card number encryption using aes-ctr mode
Credit card account numbers are 16 digits today only by convention. The ISO standard (7314?) permits card numbers up to 22 digits in length. I've seen some debit card account numbers that are already up to 19 digits in length. I wouldn't recommend coupling the encryption mechanism to an arbitrary attribute controlled by 12,000 random bankers.
Mar
19
reviewed Leave Open AES encryption takes more time to decrypt than encrypt
Mar
19
answered Deciphering text encrypted with a changing cipher
Mar
13
reviewed Approve diffusion tag wiki excerpt
Mar
12
reviewed Approve what is the current actual budget - as of 2015 - needed to build a DES breaker machine?
Mar
11
reviewed Close Fault encryption attack on RSA
Mar
11
reviewed Leave Open Affine transformation in finite field SubBytes
Mar
11
reviewed Close How to compute accumulated values in bilinear map accumulators
Mar
11
answered Known plaintext, unknown 128 bit block cipher
Mar
11
reviewed Leave Open Known plaintext, unknown 128 bit block cipher
Mar
11
reviewed Close Decrypting DES with decrypted and encrypted data
Feb
3
reviewed Close What is the difference between a hash function and a pseudorandom function?
Feb
3
answered What is the difference between a hash function and a pseudorandom function?
Jan
24
reviewed Leave Open Fairness in cryptography
Jan
24
comment Fairness in cryptography
By fair, do you mean "cheat proof", where user A might transfer his last bit but not get the final bit in return from user B? Can you edit the question to clarify it?
Jan
24
reviewed Leave Open display an image encrypted with ECB
Jan
11
reviewed No Action Needed Is there a client-side program to cryptography a HTML page and decode if correct password is writen?