FAQ
TL;DR: Sectors 1–15 are zeroed and “The file itself is certainly not a valid photo,” so JPEG headers are gone; after a hard reset, keys are missing. If you ask “how do I fix this,” try header repair only if data exists past the header. [Elektroda, mati211p, post #17194590]
Why it matters: This FAQ is for Samsung/Android users troubleshooting unreadable SD‑card photos after encryption/decryption and a factory reset.
Quick Facts
- Factory reset deletes device-stored decryption keys; SD-card data encrypted by the phone becomes unreadable without those keys. [Samsung — Encrypt SD card]
- A valid JPEG starts with the signature bytes FF D8 FF; missing headers prevent viewers from opening the image. [Kessler, 2023]
- Samsung Evo Plus 32GB card is rated up to 95 MB/s read (UHS‑I); speed isn’t the cause of post‑reset unreadable photos. [Samsung EVO Plus 32GB — Product Spec]
- Adoptable storage encrypts the SD card with a device-specific key; after reset, content remains cryptographically bound to that device. [Android Developers — Adoptable Storage]
- “Without the proper key, decryption is computationally infeasible,” so recovery can’t break encryption. [NIST, 2007]
Why can’t I open some photos on my Samsung Evo Plus after a hard reset?
Because the reset erased the device’s encryption keys. Any SD-card files still encrypted by the phone remain unreadable. If you decrypted only some files beforehand, those open, while others do not. This presents as visible filenames and sizes but blank or unopenable images. Decrypt the SD card on the original device before resetting to avoid this. If already reset, only truly decrypted or never-encrypted files can be opened. [Samsung — Encrypt SD card]
Can I recover encrypted photos after a factory reset?
Not without the original decryption keys. “Without the proper key, decryption is computationally infeasible.” If a file was fully decrypted before the reset, standard recovery may work. If it remained encrypted, no software or lab can break strong encryption. Focus recovery efforts on files proven decrypted or unencrypted. Consider backups, cloud copies, or previous device exports. [NIST, 2007]
What does “file doesn’t have the right header” mean for JPEGs?
JPEGs must start with the SOI signature FF D8 FF. If the header is missing or altered, viewers reject the file. Header damage can happen if the first sectors are zeroed or decryption failed at the start of the file. You can sometimes rebuild a header using a known-good JPEG from the same camera model. Success depends on whether required tables still exist in the data. [Kessler, 2023]
How do I check if my JPEG header is missing or wrong?
- Copy the file to a PC and open it in a hex editor.
- Confirm the first bytes are FF D8 FF (JPEG SOI).
- Compare early segments with a working photo from the same phone.
If the file begins with zeros or random data instead of FF D8 FF, the header is damaged or absent. Stop writing to the card before further analysis or recovery attempts. [Kessler, 2023]
I can see file name, size, and date, but the photo won’t open—what’s happening?
The directory entry exists, but the file content is damaged or still encrypted. In samples like yours, the beginning of the file isn’t a valid photo header, so apps can’t parse it. Sometimes the later data block is intact, but the start is chaff or zeroed. Header repair may help only when real image data follows soon after. [Elektroda, KodIT, post #17195941]
Why are my songs and videos fine, but some photos are not?
Only items encrypted by the device are locked to its keys. Media that was never encrypted—or was fully decrypted before the reset—remains editable and movable. Photos left encrypted lose their decryption keys after a factory reset and won’t open. This mismatch explains why some media works and some does not after reset. [Samsung — Encrypt SD card]
Does the Samsung Evo Plus 32GB card cause this, or is it the phone?
It’s the phone’s encryption state, not the card. The Evo Plus 32GB is rated up to 95 MB/s read, which doesn’t affect decryptability. Replacing the card won’t restore missing keys. Focus on whether files were fully decrypted before the reset. Speed or brand won’t fix header loss or missing keys. [Samsung EVO Plus 32GB — Product Spec]
The sample starts with zeros until sector 16—can a header rebuild help?
Possibly, if authentic JPEG data and required tables exist after the missing header. A header transplant from a matching camera photo can sometimes make the file parse. If essential tables or markers are gone, repair fails. Inspect with a JPEG analyzer to verify segment structure before attempting edits. [JPEGsnoop — JPEG File Decoding]
What recovery tools should I try once I’m sure files are decrypted?
Use PhotoRec to carve unencrypted photos by signature from the SD card. It ignores the filesystem and targets known headers. It cannot decrypt data, so it only recovers truly unencrypted content. Recover to a different drive, not the SD card. Preview recovered images before saving everything to reduce clutter. [PhotoRec — CGSecurity]
How do I avoid losing photos next time when encrypting SD cards?
Before any factory reset, decrypt the SD card on the phone that encrypted it. Back up all photos to a PC or cloud and verify they open. Only reset after confirming backups. If needed, re‑encrypt later. This avoids losing keys and guarantees readable copies. [Samsung — Encrypt SD card]
What’s adoptable storage, and does it change recovery options?
Adoptable storage treats the SD card as internal storage, encrypting it with a device-specific key. Data remains bound to that device and key. After a reset, or on another phone, the card’s content is unreadable without the original key. Recovery tools cannot bypass that encryption. [Android Developers — Adoptable Storage]
How can I share a sample privately while protecting my data?
Choose a non-sensitive example or share only the file’s first portion for header analysis. Strip metadata before sharing using ExifTool (example: exiftool -all= file.jpg). Do not post entire personal images publicly. Provide hashes and context, including camera model and when the issue began. [ExifTool Documentation]
Are files with zeroed first sectors recoverable, or is this a dead end?
If the zeroed region removed the SOI and critical segments like quantization and Huffman tables, decoders can’t reconstruct the image. In that case, header swaps won’t help. If those structures survive later in the file, limited repair may still work. This is an edge case where success varies. [Wikipedia: JPEG]
