Information Security, How safe is 128 bit Key?
INFORMATION SECURITY
Constitutes of 4 parts.
- A. Secrecy/Confidentiality/Encryption
- B. Authentication: whom you are talking to before revealing sensitive information
- C. Nonrepudiation: Sender cannot deny that he has not sent the message.
- D. Integrity: message you received was really the one sent and not something that a malicious adversary Encryption + Integrity
Why DL layer encryption/Link Encryption is not good idea?
- With this approach packets have to be decrypted at each router, leaving them vulnerable to attacks from within the router.
Cryptanalysis: Breaking ciphers.
Kerckhoff’s principle: Whole world should know how crypto algorithm works, All algorithms must be public. Algorithm is parameterized by key only the keys are secret
How safe is 128 bit Key?
The longer the key, higher work to be done by breaking algo. {Email: 64-bit keys will do, Commercial applications: 128 bits, Govt org: 256 bits}
bits No of Unique keys
2 4
3 8
32 4,294,967,296 (4 billion)
64 18,446,744,073,709,551,616 (18 Quintillion keys)
128 340,282,366,920,938,463,463,374,607,431,768,211,456
( 340,282,366,920,938,463,463 Quintillion keys)
1 super computer Operations
- Per Sec = 10^17 FLOPS (a hundred quadrillion FLOPS floating point operations per second).
- Per Min = 60 x 10^17
- Per Hour = 60 x 60 x 10^17
- Per Day = 24 x 60 x 60 x 10^17
- Per Month = 30 x 24 x 3600 x 10^17
- Per Year = 12 x 30 x 24 x 3600 = 31,104,000 x 10^17= 31,104,00 Quintillion
340,282,366,920,938,463,463 / 31,104,000 = 109,401,481,134,561 (approx) = 109 Trillion
109 Trillion super computers working parallelly for 1 year can break produce all combinations of 128 bit key
Types of CIPHER ALGORITHMS?
- 1. Block Ciphers(Mostly used): Encrypt block of characters
- 2. Stream Ciphers(Obsolete): Encrypt Single character at a time.
How Encryption is performed at H/W Level?
ONLY POSITION OF BITS ARE CHANGED
- A. PERMUTATION/P-BOX/TRANSPOSITION BOX: Perform internal transposition(change place) and do it at practically the speed of light since no computation is involved, just signal propagation. Internal wiring is not known to world.
- B. SUBSTITUTION/S-BOX: This can have multiple stages of P-box inside providing more complex method bit position shifting.
Product Cipher: Actual Cipher can use multiple P,S box stages inside to provide better cryptography. With large number of stages output can be a complicated function of the input. Actual implementations have minimum of 10 stages.
There are more P-boxes at start and end, called Rounds.
