# US 2009/0022309 A1 · Method of providing text representation of a cryptographic value

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- Number: US 2009/0022309 A1
- Document ID: US20090022309A1
- Status: Published application
- Kind: A1
- Application number: 12/171,398
- Filed: 2008-07-11
- Published: 2009-01-22
- Earliest claimed: 2007-07-17
- Assignees: Certicom Corp.
- Inventors: Scott A. Vanstone; Daniel R. Brown
- Web page: https://patentgrep.com/patent/US20090022309A1

## CPC

- H04L 9/3073: {involving pairings, e.g. identity based encryption [IBE], bilinear mappings or bilinear pairings, e.g. Weil or Tate pairing}
- G06F 40/151: Transformation
- H04L 2209/16: Obfuscation or hiding, e.g. involving white box
- H04L 2209/30: Compression, e.g. Merkle-Damgard construction
- H04L 2209/608: Watermarking
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

A method of representing crytographic values in text form is described. The text representation is formed from words selected from a vocabulary, which may include a collection of pseudowords. The text representations can be further transformed to a paragraph in an apparently grammatically correct form.

## Claims

### Claim 1

A method of communicating a cryptographic value to a human user, said method comprising:
selecting a vocabulary;
representing the cryptographic value as a bit string;
converting the bit string to a text using words selected from said vocabulary in accordance with a pre-determined loss-less relationship; and
communicating the text to the human user.

### Claim 2 (depends on 1)

The method of claim 1, wherein the step of representing the cryptographic value as a bit string comprises the steps of:
(a) selecting a secret value;
(b) performing a cryptographic operation on said secret value to generate the cryptographic value;
(c) determining whether a trial bit string corresponding to the cryptographic value satisfies a pre-determined criteria;
(d) repeating the sequence of steps (a) to (c) until the trial bit string satisfies the pre-determined criteria; and
(e) assigning said trial bit string to said bit string.

### Claim 3 (depends on 1)

The method of claim 1, wherein the vocabulary comprises a plurality of pseudowords.

### Claim 4

A method of communicating a public key of a recipient to users of an identity-based encryption (“IBE”) system, said method comprising:
selecting a vocabulary;
representing the public key as a bit string;
encoding the bit string to a text following a reverse arithmetic encoding algorithm utilizing words selected from the vocabulary; and
communicating the text to the recipient as an identity of the recipient.

### Claim 5 (depends on 4)

The method of claim 4, wherein the public key belongs to a private/public key pair defined on an elliptic curve of order n and with a generator g, and the step of representing the public key comprises the steps of:
(a) initializing the public key and a corresponding private key, said private key being selected randomly from [1,n);
(b) determining whether the public key satisfies a compression criteria; and
(c) if the compression criteria is not satisfied, incrementing the private key by 1, incrementing the public key by g and repeating the steps (b) to (c) until the compression criteria is satisfied.

### Claim 6

A method of communicating a cryptographic value to a user, said method comprising:
selecting a vocabulary;
representing the cryptographic value as a bit string;
converting the bit string to grammatically correct text formed of words selected from said vocabulary; and
communicating said grammatically correct text to said user.

### Claim 7 (depends on 6)

The method of claim 6, wherein the step of converting the bit string comprises the steps of:
(a) dividing the bit string into at least a first section, a second section and a third section;
(b) selecting a sentence type based on values of the first section;
(c) selecting verb form based on values of the second section;
(d) selecting words for constructing a grammatically correct sentence based on values of a first portion of the third section; and
(e) constructing the grammatically correct sentence from the selected sentence type, the selected verb form, and the selected words.

### Claim 8 (depends on 7)

The method of claim 7, wherein the step of converting the bit string comprises further the steps of:
subtracting the first portion from the third section to obtain a second portion;
upon determining said second portion to be of a positive length, repeating the steps (a) to (e) to convert said second portion to additional grammatically correct text and appending said additional grammatically correct text to said grammatically correct text formed in previous steps (a) to (e),
wherein in said repeated steps (a) to (e), said second portion is used in place of said bit string.

### Claim 9 (depends on 1)

A method of signing a message by a user, comprising the steps of:
computing a hash value of said message;
converting said hash value to a text using a conversion method according to claim 1;
receiving an audio recording, said audio recording capturing voice signal generated by the user reciting said text;
wherein said audio recording is used as a signature of said message signed by the user.

### Claim 10 (depends on 9)

The method of claim 9, wherein the hash value is computed using a secure hash function.

### Claim 11 (depends on 6)

A method of signing a message by a user, comprising the steps of:
computing a hash value of said message;
converting said hash value to a text using a conversion method according to claim 6;
receiving an audio recording, said audio recording capturing voice signal generated by the user reciting said text;
wherein said audio recording is used as a signature of said message signed by the user.

### Claim 12 (depends on 11)

The method of claim 11, wherein the hash value is computed using a secure hash function.

### Claim 13

A method of transmitting an encrypted message, comprising the steps of:
selecting a vocabulary;
representing the encrypted message as a bit string;
converting the bit string to grammatically correct text formed of words selected from said vocabulary;
selecting an embedding text;
embedding said covertext in said embedding text to generate a steganographic message; and
transmitting said steganographic message containing said covertext.

### Claim 14 (depends on 13)

The method of claim 13, wherein the step of converting the bit string comprises the steps of:
(a) dividing the bit string into at least a first section, a second section and a third section;
(b) selecting a sentence type based on values of the first section;
(c) selecting verb form based on values of the second section;
(d) selecting words for constructing a grammatically correct sentence based on values of a first portion of the third section; and
(e) constructing the grammatically correct sentence from the selected sentence type, the selected verb form, and the selected words.

### Claim 15 (depends on 14)

The method of claim 14, wherein the step of converting the bit string comprises further the steps of:
subtracting the first portion from the third section to obtain a second portion;
upon determining said second portion to be of a positive length, repeating the steps (a) to (e) to convert said second portion to additional grammatically correct text and appending said additional grammatically correct text to said grammatically correct text formed in previous steps (a) to (e),
wherein in said repeated steps (a) to (e), said second portion is used in place of said bit string.

### Claim 16 (depends on 1)

A method of hiding a secret text in a proper text, comprising the steps of:
identifying modifiable parts of the proper text to generate a list of choices, said modifiable parts comprising grammatical and vocabulary changes to the proper text based on said list of choices, said changes preserving meanings of the proper text;
converting said list of choices to a bit string;
assigning a cryptographic value to said bit string;
converting said cryptographic value to a text using a conversion method according to claim 1; and
modifying said modifiable parts using words from said text to obtain a watermarked proper text.

### Claim 17 (depends on 16)

The method of claim 16, wherein the secret text is a character string for uniquely identifying the proper text.

### Claim 18 (depends on 17)

The method of claim 17, wherein the character string is a serial number.