Key Generation Algorithm Digital Signature

/ Comments off

Feb 23, 2018 Digital Signature: If the Sender Private key is used at encryption then it is called digital signature. This digital Signature is implemented two approaches 1) RSA Approach 2) DSS Approach. A digital signature algorithm allows an entity to authenticate the integrity of signed data and the identity of the signatory. The recipient of a signed message can use a digital signature as evidence in demonstrating to a third party that the signature was, in fact, generated by the claimed signatory. Request PDF Biometric Digital Signature Key Generation and Cryptography Communication Based on Fingerprint A digital signature is a term used to describe a data string which associates a. Feb 23, 2018  Digital Signature: If the Sender Private key is used at encryption then it is called digital signature. This digital Signature is implemented two approaches 1) RSA Approach 2) DSS Approach. Elliptic Curve Digital Signature Algorithm (ECDSA) is a version of DSA using elliptic curves. In this paper, I will introduce ECDSA and discuss its key gen-eration, signing, and verifying procedures. Then, I will compare this algorithm to the RSA digital signature algorithm and discuss its various advantages and drawbacks. Finally, I will.

-->

Version 1.3

Here's an example of how to generate Secure Boot keys (PK and others) by using a hardware security module (HSM).

You'll need to know the Secure Boot Public Key Infrastructure (PKI). For more info, see Windows 8.1 Secure Boot Key Creation and Management Guidance.

Requirements

Tools Needed

  • certreq.exe – Available Inbox

  • certutil.exe – Available Inbox

  • Signtool.exe – Available in the latest Windows SDK

Hardware Security Module (HSM)

The whitepaper demonstrates the key generation using examples from the nCipher (now Thales) PCI HSM model nC1003P/nC3023P/nC3033P and the SafeNet Luna HSMs. Most of the concepts apply to other HSM vendors as well.

For other HSMs, contact your manufacturer for additional instructions on how to tailor your approach with the HSM Cryptographic Service Provider (CSP).

Approach

We use the Microsoft certificate creation tool: certreq.exe to generate the Secure Boot Platform Key (PK) and other keys needed for Secure Boot.

The certreq tool can be adapted to use an HSM by providing the Cryptographic Service Provider (CSP) to be the HSM.

Find the Cryptographic Service Provider (CSP)

You can use either the certutil.exe tool or a tool used by the HSM to list the CSPs.

  • This example uses the certutil tool to show the CSPs on the Thales/nCipher HSM:

    For the SHA-256 digesting algorithm, use the CNG provider: 'nCipher Security World Key Storage Provider'. Legacy providers do not support SHA-256 and are not suitable for use with Secure Boot.

  • This example uses the built-in Thales/nCipher tool to list the CSP:

    For the SHA-256 digesting algorithm, use the CNG provider: 'nCipher Security World Key Storage Provider'. Legacy providers do not support SHA-256 and are not suitable for use with Secure Boot.

  • This example uses the SafeNet Luna HSMs tool to list the CSP:

    For SHA-256 digest algorithm you will need to use a CNG provider – “SafeNet Key Storage Provider”. Legacy providers do not support SHA-256 and are not suitable for use with Secure Boot.

To generate the key:

Sample request.inf file:

Update the following values:

  • Subject: Replace the TODO’s with real data 'CN=Corporation TODO Platform Key,O=TODO Corporation,L=TODO_City,S=TODO_State,C=TODO_Country'.

  • ValidityPeriod, ValidityPeriodUnits: Use the validity period of 6 years. While a PK may only be valid for 2 years, the 6-year period allows for potential future servicing.

  • KeyContainer: Enter the container id that you used to create the Key with the HSM. You may be asked to provide the tokens that you have used to create the Security World for the Thales HSM.

Validating certificate (self-signed)

Verify that the certificate has been generated correctly:

For example: certutil -store -v my '7569d364a2e77b814274c81ae6360ffe'

Sample output:

Backing up the certificate

Back up your certificates. This way, if either the certificate store or the server goes down, you can add the certificate back to the store. For more info on certreq.exe, see Advanced Certificate Enrollment and Management: Appendix 3: Certreq.exe Syntax

Note, the PK is a self-signed certificate, and is also used to sign the KEK.

There are 2 parts to PK signing / initial provisioning. Please talk to your Microsoft contact to get these scripts:

  • subcreate_set_PK_example_initial_provisioning_example.ps1. Used by the signtool to sign the PK comes later in the servicing case.

  • subcreate_set_PK_service_example.ps1. Since we are dealing with the HSM case, the following line applies in the script applies.

Signing with PK certificate (servicing scenario)

This section applies to signing with your PK certificate and may not be applicable for initial provisioning of system. However, you can use the method here to test your service scenario.

Determine the certificate hash (sha1)

Determine the SHA1 hash of the certificate. You can get the SHA1 hash by using either of the following methods:

  • In Windows, open the Certificate file, select the Details tab, and check the value for Thumbprint.

  • Or use the following command:

    Sample output:

Sign with signtool with the certificate store specified as a reference

/linux-generate-ssh-key-script.html. Use the SHA1 hash to sign the KEK certificate:

Where KEK.bin is the filename of the binary certificate you want to sign.

Sample output:

NOTE For compatibility with the UEFI Specification and maximum compatibility across UEFI implementations, the /p7co and /p7ce parameters must be present, the value passed to /p7co must be 1.2.840.113549.1.7.1, and the value passed to /p7ce must be DetachedSignedData. Also, for improved compatibility with production signing environments, a signtool.exe commandline that fully specifies the hardware key container is as follows:

For more info, see Sign Tool (SignTool.exe) and Windows 8.1 Secure Boot Key Creation and Management Guidance.

Appendix A – Using Thales KeySafe for viewing keys

Thales KeySafe is based on a GUI.

To use KeySafe, you must have installed JRE/JDK 1.4.2, 1.5, or 1.6. Install Java before you install the nCipher software.

/aes-secret-key-generator-python.html. Configure the hardserver config file under the %NFAST_KMDATA%config folder:

Edit settings in the server_startup section:

nonpriv_port. This field specifies the port on which the hardserver listens for local non-privileged TCP connections.

  • Default to connecting to port 9000.

  • If the NFAST_SERVER_PORT environment variable is set, it overrides any value set for nonpriv_port

priv_port. This field specifies the port on which the hardserver listens for local privileged TCP connections.

  • Default to connecting to port 9001.

  • If the NFAST_SERVER_PRIVPORT environment variable is set, it overrides any value set for priv_port

The following are screenshots from the Thales KeySafe GUI:

The following image is generated by launching the KeySafe utility and then navigating to the KeyList menu.

For more info, see the nCipher/Thales Users Guide.

Appendix B: Using SafeNet CMU Utility to view keys

For more details, please consult the SafeNet Luna HSM documentation.

Related topics

  • Cryptography Tutorial
  • Cryptography Useful Resources
  • Selected Reading

Digital signatures are the public-key primitives of message authentication. In the physical world, it is common to use handwritten signatures on handwritten or typed messages. They are used to bind signatory to the message.

Similarly, a digital signature is a technique that binds a person/entity to the digital data. This binding can be independently verified by receiver as well as any third party.

Digital signature is a cryptographic value that is calculated from the data and a secret key known only by the signer.

In real world, the receiver of message needs assurance that the message belongs to the sender and he should not be able to repudiate the origination of that message. This requirement is very crucial in business applications, since likelihood of a dispute over exchanged data is very high.

Model of Digital Signature

As mentioned earlier, the digital signature scheme is based on public key cryptography. The model of digital signature scheme is depicted in the following illustration −

The following points explain the entire process in detail −

  • Each person adopting this scheme has a public-private key pair.

  • Generally, the key pairs used for encryption/decryption and signing/verifying are different. The private key used for signing is referred to as the signature key and the public key as the verification key.

  • Signer feeds data to the hash function and generates hash of data.

  • Hash value and signature key are then fed to the signature algorithm which produces the digital signature on given hash. Signature is appended to the data and then both are sent to the verifier.

  • Verifier feeds the digital signature and the verification key into the verification algorithm. The verification algorithm gives some value as output.

  • Verifier also runs same hash function on received data to generate hash value.

  • For verification, this hash value and output of verification algorithm are compared. Based on the comparison result, verifier decides whether the digital signature is valid.

  • Since digital signature is created by ‘private’ key of signer and no one else can have this key; the signer cannot repudiate signing the data in future.

It should be noticed that instead of signing data directly by signing algorithm, usually a hash of data is created. Since the hash of data is a unique representation of data, it is sufficient to sign the hash in place of data. The most important reason of using hash instead of data directly for signing is efficiency of the scheme.

Let us assume RSA is used as the signing algorithm. As discussed in public key encryption chapter, the encryption/signing process using RSA involves modular exponentiation.

Signing large data through modular exponentiation is computationally expensive and time consuming. The hash of the data is a relatively small digest of the data, hence signing a hash is more efficient than signing the entire data.

Importance of Digital Signature

Out of all cryptographic primitives, the digital signature using public key cryptography is considered as very important and useful tool to achieve information security.

Signature Algorithm

Apart from ability to provide non-repudiation of message, the digital signature also provides message authentication and data integrity. Let us briefly see how this is achieved by the digital signature −

  • Message authentication − When the verifier validates the digital signature using public key of a sender, he is assured that signature has been created only by sender who possess the corresponding secret private key and no one else.

  • Data Integrity − In case an attacker has access to the data and modifies it, the digital signature verification at receiver end fails. The hash of modified data and the output provided by the verification algorithm will not match. Hence, receiver can safely deny the message assuming that data integrity has been breached.

  • Non-repudiation − Since it is assumed that only the signer has the knowledge of the signature key, he can only create unique signature on a given data. Thus the receiver can present data and the digital signature to a third party as evidence if any dispute arises in the future.

By adding public-key encryption to digital signature scheme, we can create a cryptosystem that can provide the four essential elements of security namely − Privacy, Authentication, Integrity, and Non-repudiation.

Encryption with Digital Signature

Key Generation Algorithm Digital Signature Software

In many digital communications, it is desirable to exchange an encrypted messages than plaintext to achieve confidentiality. In public key encryption scheme, a public (encryption) key of sender is available in open domain, and hence anyone can spoof his identity and send any encrypted message to the receiver.

This makes it essential for users employing PKC for encryption to seek digital signatures along with encrypted data to be assured of message authentication and non-repudiation.

Digital Signature Algorithm In C

This can archived by combining digital signatures with encryption scheme. Let us briefly discuss how to achieve this requirement. There are two possibilities, sign-then-encrypt and encrypt-then-sign.

However, the crypto system based on sign-then-encrypt can be exploited by receiver to spoof identity of sender and sent that data to third party. Hence, this method is not preferred. The process of encrypt-then-sign is more reliable and widely adopted. This is depicted in the following illustration −

Digital Signature Algorithm

The receiver after receiving the encrypted data and signature on it, first verifies the signature using sender’s public key. After ensuring the validity of the signature, he then retrieves the data through decryption using his private key.