# US 8,416,948 B2 · System for secure variable data rate transmission

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- Number: US 8,416,948 B2
- Document ID: US8416948B2
- Status: Granted
- Kind: B2
- Application number: 12/802,306
- Filed: 2010-06-04
- Published: 2011-12-08
- Granted: 2013-04-09
- Earliest claimed: 2010-06-04
- Assignees: Leanics Corporation
- Applicants: Aaron E. Cohen; Keshab K. Parhi
- Inventors: Aaron E. Cohen; Keshab K. Parhi
- Web page: https://patentgrep.com/patent/US8416948B2

## CPC

- H04L 9/0637: {Modes of operation, e.g. cipher block chaining [CBC], electronic codebook [ECB] or Galois/counter mode [GCM]}
- H04L 9/065: {Encryption by serially and continuously modifying data stream elements, e.g. stream cipher systems, RC4, SEAL or A5/3}
- H04L 2209/60: Digital content management, e.g. content distribution
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

Secure Variable Data Rate Transceivers and methods for implementing Secure Variable Data Rate are presented. An efficient and systematic method and circuit for implementing secure variable data rate transceivers are presented. The SVDR method is based on block ciphers. An index method is presented for minimizing transmission overhead. This allows SVDR to achieve higher security by using the full ciphermode stream.

## Claims

### Claim 1

A secure variable data rate encryption method, comprising:
Receiving blocks of pseudo-random bits of block length K (K>0 and an integer);
Receiving a variable data rate packet of length V bits, such that 1<=V<=NK, where N, an integer greater than or equal to 1, is chosen to satisfy NK>=Vmax, where Vmax is the maximum of all variable data rate packet lengths;
Appending (NK−V) dummy bits at the end of the said variable data rate packet of length V bits to create an augmented packet of length NK bits,
Computing an encrypted ciphertext packet stream by exclusive-or of the augmented packet and N blocks of pseudo-random sequences each of length K bits;
Transmitting a first V bits of the encrypted ciphertext after truncating the last (NK−V) bits from the ciphertext of length NK bits.

### Claim 2 (depends on 1)

The secure variable data rate encryption method of claim 1 where the pseudorandom sequence is generated by the Advanced Encryption Standard (AES).

### Claim 3 (depends on 1)

The secure variable data rate encryption method of claim 1 where the pseudorandom sequence is generated by the Counter (CTR) mode of the AES encryption.

### Claim 4 (depends on 1)

The secure variable data rate encryption method of claim 1 where the pseudorandom sequence is generated by the Cipher Feedback (CFB) mode of the AES encryption.

### Claim 5 (depends on 1)

The secure variable data rate encryption method of claim 1 where the pseudorandom sequence is generated by the Output Feedback (OFB) mode of the AES encryption.

### Claim 6 (depends on 1)

The secure variable data rate encryption method of claim 1 implemented by a machine.

### Claim 7

A secure variable data rate decryption method comprising:
receiving blocks of pseudorandom bits of block length K (K>0 and an integer);
receiving a variable data rate packet of length V bits, such that 1<=V<=NK, where N, an integer greater than or equal to 1, is chosen to satisfy NK>=Vmax, where Vmax is the maximum of all variable data rate packet lengths;
appending (NK−V) dummy bits at the end of the said variable data rate packet of length V bits to create an augmented packet of length NK bits,
computing the decrypted ciphertext packet stream by exclusive-or of the augmented packet of length NK bits and N pseudorandom blocks each of length K bits; and
retaining a first V bits of the decrypted ciphertext after truncating the last (NK−V) bits from the decrypted ciphertext of length NK bits.

### Claim 8 (depends on 7)

The secure variable data rate decryption method of claim 7 where the pseudorandom sequence is generated by the Advanced Encryption Standard (AES).

### Claim 9 (depends on 7)

The secure variable data rate decryption method of claim 7 where the pseudorandom sequence is generated by the Counter (CTR) mode of the AES encryption.

### Claim 10 (depends on 7)

The secure variable data rate decryption method of claim 7 where the pseudorandom sequence is generated by the Cipher Feedback (CFB) mode of the AES encryption.

### Claim 11 (depends on 7)

The secure variable data rate decryption method of claim 7 where the pseudorandom sequence is generated by the Output Feedback (OFB) mode of the AES encryption.

### Claim 12 (depends on 7)

The secure variable data rate decryption method of claim 7 where the decryptor is implemented using a machine.

### Claim 13

An integrated circuit that implements a secure variable data rate encryptor, comprising:
A digital circuit;
Receiving blocks of pseudo-random bits of block length K (K>0 and an integer);
Receiving a variable data rate packet of length V bits, such that 1<=V<=NK, where N, an integer greater than or equal to 1, is chosen to satisfy NK>=Vmax, where Vmax is the maximum of all variable data rate packet lengths;
Appending (NK−V) dummy bits at the end of the said variable data rate packet of length V bits to create an augmented packet of length NK bits,
Computing an encrypted ciphertext packet stream by exclusive-or of the augmented packet and N blocks of pseudo-random sequences each of length K bits;
Transmitting a first V bits of the encrypted ciphertext after truncating the last (NK−V) bits from the ciphertext of length NK bits.

### Claim 14 (depends on 13)

The secure variable data rate encryptor of claim 13 where the pseudorandom sequence is generated by the Advanced Encryption Standard (AES).

### Claim 15 (depends on 13)

The secure variable data rate encryptor of claim 13 where the pseudorandom sequence is generated by the Counter (CTR) mode of the AES encryption.

### Claim 16 (depends on 13)

The secure variable data rate encryptor of claim 13 where the pseudorandom sequence is generated by the Cipher Feedback (CFB) mode of the AES encryption.

### Claim 17 (depends on 13)

The secure variable data rate encryptor of claim 13 where the pseudorandom sequence is generated by the Output Feedback (OFB) mode of the AES encryption.

### Claim 18

An integrated circuit that implements a secure variable data rate decryptor, comprising:
A digital circuit;
Receiving blocks of pseudorandom bits of block length K (K>0 and an integer);
Receiving a variable data rate packet of length V bits, such that 1<=V<=NK, where N, an integer greater than or equal to 1, is chosen to satisfy NK>=Vmax, where Vmax is the maximum of all variable data rate packet lengths;
Appending (NK−V) dummy bits at the end of the said variable data rate packet of length V bits to create an augmented packet of length NK bits;
Computing the decrypted ciphertext packet stream by exclusive-or of the augmented packet of length NK bits and the N pseudorandom blocks each of length K bits; and
Retaining a first V bits of the decrypted ciphertext after truncating the last (NK−V) bits from the decrypted ciphertext of length NK bits.

### Claim 19 (depends on 18)

The secure variable data rate decryptor of claim 18 where the pseudorandom sequence is generated by the Advanced Encryption Standard (AES).

### Claim 20 (depends on 18)

The secure variable data rate decryptor of claim 18 where the pseudorandom sequence is generated by the Counter (CTR) mode of the AES encryption.

### Claim 21 (depends on 18)

The secure variable data rate decryptor of claim 18 where the pseudorandom sequence is generated by the Cipher Feedback (CFB) mode of the AES encryption.

### Claim 22 (depends on 18)

The secure variable data rate decryptor of claim 18 where the pseudorandom sequence is generated by the Output Feedback (OFB) mode of the AES encryption.