Minor Project- AES Implementation in Verilog

MINOR PROJECT
ADVANCED ENCRYPTION STANDARD
ON
Presentation by:
HARDIK MANOCHA (04420902812)
NIVEDITA WASSON (05620902812)

What is encryption?
In cryptography, encryption is the process of encoding messages or
information in such a way that only authorized parties can read it.
Encryption does not of itself prevent interception, but denies the
message content to the interceptor.
In an encryption scheme, the intended communication information or
message, referred to as plaintext, is encrypted using an encryption
algorithm, generating ciphertext that can only be read if decrypted.

Advanced Encryption Standard (AES)
The Advanced Encryption Standard (AES), also known as Rijndael (its original
name), is a specification for the encryption of electronic data established by the
U.S. National Institute of Standards and Technology (NIST) in 2001.
AES is based on the Rijndael cipher developed by two Belgian cryptographers,
Joan Daemen and Vincent Rijmen,
who submitted a proposal to NIST during the AES selection process.
Rijndael is a family of ciphers with different key and block sizes.

AES is based on a design principle known as
a substitution-permutation network, combination of both substitution and
permutation, and is fast in both software and hardware.
The algorithm described by AES is a symmetric-key algorithm, meaning the
same key is used for both encrypting and decrypting the data.
The Rijndael specification per se is specified with block and key sizes that may be
any multiple of 32 bits, both with a minimum of 128 and a maximum of 256 bits.
AES is a variant of Rijndael which has a fixed block size of 128 bits, and a key size
of 128, 192, or 256 bits.

Description of the cipher
AES operates on a 4×4 column-major order matrix of bytes, termed the
state, although some versions of Rijndael have a larger block size and have
additional columns in the state.
For instance, if you have 16 bytes, b0,b1,...,b15, these
bytes are represented as this matrix:

The key size used for an AES cipher specifies the number of repetitions of
transformation rounds that convert
the input, called the plaintext,
into the final output, called the ciphertext.
The number of cycles of repetition are as follows:
 10 cycles of repetition for 128-bit keys.
Each round consists of several processing steps, each containing four similar but
different stages, including one that depends on the encryption key itself.
A set of reverse rounds are applied to transform ciphertext back into the original
plaintext using the same encryption key.

PERFORMANCE
High speed and low RAM requirements were criteria of the AES selection
process. Thus AES performs well on a wide variety of hardware, from 8-bit smart
cards to high performance computers.
On a Pentium Pro, AES encryption requires 18 clock cycles per byte,[40] equivalent
to a throughput of about 11 MB/s for a 200 MHz processor.
On a 1.7 GHz Pentium M throughput is about 60 MB/s.
On Intel Core i3/i5/i7 and AMD APU and FX CPUs supporting AES-NI instruction set
extensions, throughput can be over 700 MB/s per thread.

APPLICATIONS
AES has been adopted by the U.S. government and is now used worldwide.
In the United States, AES was announced by the NIST as U.S. FIPS PUB 197 (FIPS 197)
on November 26,2001. This announcement followed a five-year standardization process
in which fifteen competing designs were presented and evaluated, before the Rijndael
cipher was selected as the most suitable.
AES became effective as a federal government standard on May 26, 2002 after approval
by the Secretary of Commerce.
AES is included in the ISO/IEC 18033-3 standard.
AES is available in many different encryption packages, and is the first publicly
accessible and open cipher approved by the National Security Agency (NSA) for top
secret information when used in an NSA approved cryptographic module.

SECURITY
Until May 2009, the only successful published attacks against the full AES were side
channel attacks on some specific implementations. Side-channel attacks do not
attack the underlying cipher, and thus are not related to security in that context.
They rather attack implementations of the cipher on systems which inadvertently
leak data.
The National Security Agency (NSA) reviewed all the AES finalists, including
Rijndael, and stated that all of them were secure enough for U.S. Government non-
classified data. In June 2003, the U.S.
Government announced that AES could be used to protect classified information.
AES has 10 rounds for 128-bit keys, 12 rounds for 192-bit keys, and 14 rounds for
256-bit keys.
By 2006, the best known attacks were on 7 rounds for 128-bit keys, 8
rounds for 192-bit keys, and 9 rounds for 256-bit keys.

DESCRIPTION
OF
THE ALGORITHM
FOR
AES

AES Conceptual Scheme
AESAES
Plaintext (128 bits)
Cipher text (128 bits)
Key (128-256 bits)

Multiple rounds
 Rounds are (almost) identical
 First and last round are a little different

High Level Description
No MixColumns

128-bit values
 Data block viewed as 4-by-4 table of bytes
 Represented as 4 by 4 matrix of 8-bit bytes.
 Key is expanded to array of 32 bits words
1 byte

SubBytes: Byte Substitution
 A simple substitution of each byte
 provide a confusion
 Uses one S-box of 16x16 bytes containing a permutation of all 256 8-
bit values
 Each byte of state is replaced by byte indexed by row (left 4-bits) &
column (right 4-bits)
 e.g. byte {95} is replaced by byte in row 9 column 5
 which has value {2A}
 S-box constructed using defined transformation of values in Galois
Field- GF(28
)

SubBytes Operation
The SubBytes operation involves 16 independent byte-to-byte transformations.
• Interpret the byte as two hexadecimal digits xy
• SW implementation, use row (x) and column (y) as lookup pointer

SubBytesTable
Implement byTable Lookup

Sample SubByteTransformation
The SubBytes and InvSubBytes transformations are inverses of each other.

ShiftRows
 Shifting, which permutes the bytes.
 A circular byte shift in each each
 1st
row is unchanged
 2nd
row does 1 byte circular shift to left
 3rd row does 2 byte circular shift to left
 4th row does 3 byte circular shift to left
 In the encryption, the transformation is
called ShiftRows
 In the decryption, the transformation is
called InvShiftRows and the shifting is to the
right

MixColumns
 ShiftRows and MixColumns provide diffusion to the cipher
 Each column is processed separately
 Each byte is replaced by a value dependent on all 4 bytes in
the column
 Effectively a matrix multiplication in GF(28
) using prime poly
m(x) =x8
+x4
+x3
+x+1

AddRoundKey
 XOR state with 128-bits of the round key
 AddRoundKey proceeds one column at a time.
adds a round key word with each state column matrix
the operation is matrix addition
 Inverse for decryption identical
since XOR own inverse, with reversed keys
 Designed to be as simple as possible

AES Key Scheduling
Takes 128-bits (16-bytes) key and expands into array of 44 32-bit words.

References
Federal Information Processing Standards Publication 197
November 26, 2001 Specification for the ADVANCED ENCRYPTION STANDARD (AES)
https://en.wikipedia.org/wiki/Advanced_Encryption_Standard?oldid=683906082
Daemen Joan and Rijmen Vincent (1999) The Rijndael Block Cipher AES Version 2

Minor Project- AES Implementation in Verilog

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