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Sign and verify data using a key in Azure Key Vault with JavaScript

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Create the KeyClient with the appropriate programmatic authentication credentials, then create a CryptographyClient use the client to set, update, and rotate a key in Azure Key Vault.

Signing data

A few suggestions for signing data:

  • Hash large data before signing
  • Hash one-way data before signing such as passwords
  • Small 2-way data can be signed directly

Sign and verify large or one-way data with key

To sign and verify your digested message, use the following methods:

For digested messages:

  • sign to sign the digest of a message. This is useful for large data or one-way data such as passwords.
  • verify to verify the digest of a message.
import { createHash } from "crypto";
import { DefaultAzureCredential } from '@azure/identity';
import {
  CryptographyClient,
  KeyClient,
  KnownSignatureAlgorithms
} from '@azure/keyvault-keys';

// get service client
const credential = new DefaultAzureCredential();
const serviceClient = new KeyClient(
    `https://${process.env.AZURE_KEYVAULT_NAME}.vault.azure.net`,
    credential
);

// get existing key
const keyVaultKey = await serviceClient.getKey('MyRsaKey');

if (keyVaultKey?.name) {

    // get encryption client with key
    const cryptoClient = new CryptographyClient(keyVaultKey, credential);
    
    // get digest
    const digestableData = "MyLargeOrOneWayData";
    const digest = createHash('sha256')
      .update(digestableData)
      .update(process.env.SYSTEM_SALT || '')
      .digest();
    
    // sign digest
    const { result: signature } = await cryptoClient.sign(KnownSignatureAlgorithms.RS256, digest);
   
    // store signed digest in database

    // verify signature
    const { result: verified } = await cryptoClient.verify(KnownSignatureAlgorithms.RS256, digest, signature);
    console.log(`Verification ${verified ? 'succeeded' : 'failed'}.`);
}

Sign and verify small data with key

To sign and verify your data, use the following methods:

For data:

import { createHash } from "crypto";
import { DefaultAzureCredential } from '@azure/identity';
import {
  CryptographyClient,
  KeyClient,
  KnownSignatureAlgorithms
} from '@azure/keyvault-keys';

// get service client
const credential = new DefaultAzureCredential();
const serviceClient = new KeyClient(
    `https://${process.env.AZURE_KEYVAULT_NAME}.vault.azure.net`,
    credential
);

// get existing key
const keyVaultKey = await serviceClient.getKey('MyRsaKey');

if (keyVaultKey?.name) {

    // get encryption client with key
    const cryptoClient = new CryptographyClient(keyVaultKey, credential);
    
    const data = 'Hello you bright big beautiful world!';
    
    // sign
    const { result: signature } = await cryptoClient.signData(
        KnownSignatureAlgorithms.RS256,
        Buffer.from(data, 'utf8')
    );
    
    // verify signature
    const { result: verified } = await cryptoClient.verifyData(
        KnownSignatureAlgorithms.RS256,
        Buffer.from(data, 'utf8'),
        signature
    );
    console.log(`Verification ${verified ? 'succeeded' : 'failed'}.`);
}

Next steps