[Bug] SD card access speed is only 7Mb/s when encryption is enabled

[pribambas]

I use Samsung EVO+ microSDXC 256GB card. When SD card encryption is activated in Settings, read/write access speed to the SD card is about 7Mb/s which is too slow. Without SD card encryption I got 40Mb/s for write and 70Mb/s for read and these speeds are rather acceptable. How can I get at least 40Mb/s with enabled encryption?

I tested speeds by copying a 1Gb file from the internal storage to the SD card and back. I tried several file managers from Play and also ADB shell:
time cp /storage/emulated/0/1gbfile /storage/0D49-786B/

Needless to say that the internal storage is also encrypted and nevertheless it's very fast. I guess a hardware acceleration might be missed for SD encryption, but 7Mb/s is slow even for pure software implementation. Please invite a kernel dev representative to the thread. Thanks.

[pribambas]

Anybody from Sony devs. Couldn't you explain why is encrypted SD card access is so slow? Are there any plans to fix this? Thanks.

[pribambas]

Write speed from PC to XZP's SD-card over USB3.0

SD-card encryption enabled: 8.8Mb/s

SD-card encryption disabled: 31Mb/s

[Qatrium]

@pribambas

I'm not a dev, but logically there's nothing wrong with the symptoms you're describing. An encrypted SD card will be slower on file transfer as it's reading + encrypting + writing at the same time. So the encryption process is what is taking the extra time.

[pribambas]

 @Quester

First of all 31Mb/s of unencrypted access is too slow for a SD card that shows 70Mb/s of real write speed on another device. It seems to me there is a hardware bottleneck in XZP that couldn't be fixed by software updates. Ok, I don't expect a fix for unencrypted write speed.

But with modern hardware encryption engines we may expect speeds of tens or even hundreds megabytes per second. So I expect encrypted write speed to be at least not lower than the unencrypted one. Even 6-years old marvell chips for NAS were able to do AES with 10Mb/s.

Moreover internal storage is also encrypted, but it's still much faster than even unencrypted SD-card.

So there is something to fix with SD-card encryption and I expect a software update from Sony that will fix it.

[najodleglejszy]

internal storage is fast despite being encrypted because of the CPU being specifically made to support encryption (as required by Google). before that was a thing, encrypting your device resulted in a performance hit. perhaps it's that kind of an issue with the external storage.

[pribambas]

---

@najodleglejszy wrote:
the CPU being specifically made to support encryption

---

Yes, but nothing stops Sony or any other vendor from using this CPU/hardware assistance for encrypting SD card, SSL or VPN traffic or anything else. There may be a limited number of hardware-assisted encryption/hashing algorithms, but why not selecting an assisted algorithm for SD card?

[pribambas]

45.0.A.7.137

I've retested. About 10Mb/s copying from internal storage to SD card. Still tooooo slow

[pribambas]

Sony, are you going to fix slow SD card encryption?

[pribambas]

The oreo update (47.1.A.3.254) didn't fix the SD card encryption speed issue. It's still too slow 7-10Mb/s read/write for a high performance UHS-I card.