ATA Secure Erase is an optional security feature implemented by many flash-based disk devices specifically because write degradation and overprovisioning preclude them from being wiped via overwrite as you would magnetic media.
More SSD disk controllers than you may realize have an AES encryption engine and persistent storage for the key. The controller is encrypting/decrypting on the fly transparent to the user/system. A secure erase simply rolls that key (and flags all the cells as empty).
As noted in the sibling comment, there must be trust in the device itself that the old key is unrecoverable (or the data recoverable if the prior key had been compromised).
hdparm on any linux liveusb (e.g. Clonezilla) and an eSATA dock and you can nuke a few disks a minute with two commands:
hdparm --user-master u --security-set-pass p /dev/sdX
hdparm --user-master u --security-erase-enhanced p /dev/sdX
The other standard is TCG's OPAL. An AES media encryption key (MEK) is generated to encrypt/decrypt all data on the fly. The MEK is encrypted with a user-defined key encrypting key (KEK) and that encrypted MEK is stored on the drive. At boot the user (or some external process) needs to supply the drive with the KEK to decrypt the MEK and begin transparently decrypting/encrypting data on the fly. Splitting the disk into multiple "locking ranges" with independent MEKs and KEKs is also described in the spec enabling secure wipe of just a portion of the disk. Lose the KEK or destroy the MEK and the data is unrecoverable.
I'd say this option still requires trust in the disk itself but since TCG dictates not just the interface but also the implementation and has a corresponding certification process (as well as reliance on an off-device key), I reckon TCG OPAL devices should be more trusted than those that simply claim to implement the ATA Secure Erase command, but I haven't had an opportunity to test any.
It's interesting that even the drives themselves use this strategy to "erase" data; it doesn't actually overwrite the cells, it just always encrypts all data that goes to cells and rotates the key when it's asked to erase. This strategy is clearly superior, it doesn't cost any wear on the cells to perform, and it's instant.
The multiple locking ranges is pretty neat, I'd never heard of that.
* If any part of a block is found to be corrupted for any reason, the block is transparently set aside and never used again, but its contents may still be present to read for someone that is willing to bypass the drive's firmware.
* To prevent uneven wear, ssd capacity is over provisioned which means it has more cells than what it tells the OS. In general, when you "overwrite" a block on your drive, that data likely does not actually overwrite the cell where the data used to be. The drive picks some other unused cell, writes the data there, and does some bookkeeping so it knows that this new cell is what the OS means when it asks for that block again. When the OS "fills the disk" it may not end up overwriting some of those cells due to the firmware's arbitrary wear leveling algorithm.
* Many drives have a local write buffer that uses different, faster persistent storage to temporarily save writes to the drive as it takes its time to write out cells. This is to prevent data loss in the case of a power outage. In case the drive hadn't fully written all the blocks to the main storage when it boots back up again, it finds the data in the write buffer and finishes the job. The write buffer has both of the previous issues except its even more arbitrary and depends on load profile which your random filling routine is not guaranteed to hit.
There is no such thing as securely overwriting blocks anymore, because "blocks" are a fiction presented to your OS by the drive's firmware. There is only one way to be sure the data on the drive is filled with random data: make it random to begin with, and ensure that it stays random by destroying the decryption key.
How useful is one block of recovered data?
Edit: HDDs typically have 4K blocks though ("advanced-format drives"), but we're not talking about HDDs.
But yeah, it depends on the manufacturer of the drive, so you don't want to take the chance, Full encryption is unbeatable.
Extra cells are used both reactively and proactively.
Reactively: Error when erasing or write/verifying a cell? Copy contents to spare cell, flag old cell as bad, update the map, maybe complain if running low on spare cells but otherwise call it a day.
Proactively: Cells are only rated for so many erase operations which directly informs the longevity (total bytes written) of a drive. MLC cells can be written to 3,000 times and SLC 20,000 but the latter is much more expensive. For use cases where greater longevity is required (without spending SLC money), why not put a disk together that has twice as many cells as it needs and wear level across all of them? If you `dd if=/dev/zero of=/dev/sdX bs=64k status=progress` your 32GB drive and it'll complete after 32GB but you have no way of knowing how many more cells that drive has that you didn't touch.
(Also as one of the parents pointed out, disk controllers are getting smart. You don't know if it was transparently compressing data too causing you to touch even fewer cells. ATA Secure Erase is the way to go.)