Contents
- 1. Tag Format
- 1. IMG3
- 1. IMG3
- 2. Example Tag
The SEPO (Security Epoch) tag specifies the security epoch required for the device to load the provided image. It is believed to be used by Apple to prevent devices from loading previously vulnerable firmwares, but this is unconfirmed.
Tag Format
IMG3
Img3SepoTag {
0 u32 magic // 'OPES' ('SEPO' in little endian)
4 u32 fullSize // including header and padding
8 u32 size // including padding
C u32 value
10 u8[] padding // optional
}Example Tag
The following tag is from the AppleLogo payload from the 2.0 (build 5A347) build for the iPhone (iPhone1,1).
| Offset | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F | ASCII | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1C70 | 45 | 50 | 45 | 53 | E | P | E | S | |||||||||||||||||||||||||
| 1C80 | 10 | 00 | 00 | 00 | 04 | 00 | 00 | 00 | 04 | 00 | 00 | 00 | . | . | . | . | . | . | . | . | . | . | . | . | |||||||||
| Offset | Length | Explanation |
|---|---|---|
| 0x1C7C | 4 | magic: When interpreted in little endian order, these bytes give the string, SEPO. |
| 0x1C80 | 4 | fullSize: This tag is 0x10 (16) bytes long. |
| 0x1C84 | 4 | size: The actual payload (including padding) is 4 bytes long. |
| 0x1C88 | 4 | value: The actual value of the tag: 4. |