Cryptographic Erase Explained: When Can Encrypted Drives Be Safely Reused?

For businesses replacing laptops, refreshing storage or preparing devices for reuse it is important to know if the encrypted drive can be safely reused. One option is cryptographic erasure, an encrypted drive sanitisation method that makes encrypted data inaccessible by securely destroying the encryption key. Rather than trying to overwrite every part of an SSD, the process targets the key protecting the data. 

Before a device is considered sanitised the encryption, key management, sanitation process and verification all need to be considered. 

What is Cryptographic Erase? 

Cryptographic erase is a method of sanitising encrypted storage by making the encryption key needed to access the data unavailable.  

When information is stored on an encrypted drive, the data is protected by an encryption key. If that key is securely destroyed, the encrypted information should no longer be accessible through normal decryption. 

The process can also be known as encryption key destruction or an encryption key purge. 

Cryptographic erasure is also recognised as a NIST purge sanitisation method as it leaves the data un-decryptable. 

The process can be viewed as: 

1. Encrypted data  
2. Encryption key securely destroyed 
3. Data becomes inaccessible 

Why Use Cryptographic Erase on an SSD? 

Traditional data wiping attempts to overwrite information on a storage device. However, SSDs store data across NAND flash memory cells in ways that can make overwriting more complex. 

Therefore, crypto erase SSD works by destroying the encryption key, rendering the encrypted data unreadable. For suitable encrypted SSDs, this can provide a practical and efficient sanitisation method. 

For businesses dealing with large numbers of encrypted SSDs, this can provide a practical way to prepare suitable drives for reuse. 

Is Deleting an Encryption Key Enough to Sanitise a Drive? 

Deleting an encryption key can be effective when the drive has been appropriately encrypted and the relevant keys can be reliably destroyed. However, simply deleting a key from a system does not prove that all copies or versions of the key have been deleted.  

Businesses should understand: 

• Where the encryption keys are stored  
• Whether additional copies exist  
• Whether the drive supports secure key destruction  
• Whether the sanitisation process can be verified  
• What evidence is available afterwards 

Following recognised data destruction best practices helps businesses assess whether cryptographic erasure is appropriate and verifiable for their devices.  

What is SED Sanitisation? 

Self-encrypting drives, or SEDs are designed to encrypt all data stored on the drive.  

SED sanitisation can make the stored data inaccessible. Instead of overwriting all the data, the encryption key used to access the data is destroyed.   

This can make SEDs suitable candidates for cryptographic sanitisation. 

When Should Cryptographic Erase Not Be Used?

Knowing when not to use cryptographic erasure is just as important as knowing when it’s useful. 

The method may not be appropriate when: 

• The drive was not encrypted 
• Key management cannot be verified 
• The sanitisation process cannot be verified  
• The business requires physical destruction 

For example, if information was stored on the device before encryption was enabled then cryptographic erasure will only remove the encrypted data and addition sanitisation methods may be required.   

The sensitivity of the information should also influence the decision. As higher risk information may require a different approach depending on the business’ requirements. 

Can Cryptographically Erased Drives Be Reused? 

One of the biggest advantages of cryptographic erasure is that it can support media reuse.  

If an encrypted drive is suitable for cryptographic sanitisation and the process has been successfully completed and verified, the physical hardware may still be perfectly usable.  

Instead of destroying a functioning SSD, businesses can potentially prepare it for another device or user.  

This supports a reuse first approach and can help businesses get more value from their existing hardware.  

Redeploying Securely Sanitised Drives   

Businesses may be able to redeploy securely sanitised drives and devices once the appropriate checks have been completed.   

A typical process includes: 

1. Identify the drive and its encryption status 
2. Confirm that cryptographic erasure is suitable 
3. Perform sanitisation  
4. Complete driver verification  
5. Record the results  
6. Reconfigure the device  
7. Redeploy to its next user 

This connects both data sanitisation and reuse instead of treating them as separate activities. 

What If a Drive Cannot Be Cryptographically Erased?   

Not every drive will be suitable for this approach. Some may have unknown encryption history, unreliable security functions or physical faults.  

In these cases, businesses can consider alternative sanitisation methods, including other forms of SSD wiping and sanitisation or physical destruction.  

The aim is to choose a method that provides appropriate assurance rather than simply choosing the fastest method.  

Conclusion 

Cryptographic erase provides a different approach to data sanitisation by destroying the encryption key that protects information rather than attempting to overwrite every part of the drive.  

For suitable encrypted SSDs, this can make it possible to securely sanitise storage while keeping the physical hardware available for media reuse or redeployment.  

However, cryptographic erasure is only as reliable as the encryption key management behind it. Businesses should confirm that the method is appropriate, complete the necessary drive verification and retain evidence of the process. Whether sanitisation is carried out internally or with the support of certified data destruction services, maintain clear documentation can help demonstrate that data has been securely sanitised.