test(espsecure): Add details for generating the files present in secure_images

Author: Harshal5

test/secure_images/README.md

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+# How are the test images generated?
+
+## IV generation
+
+`{len}bit_iv.bin`
+
+```
+dd if=/dev/random of={len}bit_iv.bin bs=1 count=32
+
+where len = [256]
+```
+
+## Keys Generation
+
+### Encryption Keys
+
+`{len}bit_key.bin`
+
+```
+espsecure generate-flash-encryption-key -l {len} {len}bit_key.bin
+
+where len = [256, 512]
+```
+
+`ef-flashencryption-key.bin`
+
+```
+espsecure generate-flash-encryption-key -l 256 ef-flashencryption-key.bin
+```
+
+### Signing Keys
+
+For schemes = [rsa, ecdsa192, ecdsa256, ecdsa384]
+
+`{scheme}_secure_boot_signing_keyX.pem`
+
+```
+espsecure generate-signing-key -v 2 --scheme {scheme} {scheme}_secure_boot_signing_keyX.pem
+```
+
+`{scheme}_secure_boot_signing_key_v2.pem`
+
+```
+espsecure generate-signing-key -v 2 --scheme {scheme} {scheme}_secure_boot_signing_key_v2.pem
+```
+
+`{scheme}_secure_boot_signing_pubkeyX.pem`
+
+```
+espsecure extract-public-key -v 2 -k {scheme}_secure_boot_signing_keyX.pem {scheme}_secure_boot_signing_pubkeyX.pem
+```
+
+`{scheme}_public_key_digest_v2.bin`
+
+```
+espsecure digest-sbv2-public-key -k {scheme}_secure_boot_signing_key_v2.pem -o {scheme}_public_key_digest_v2.bin
+```
+
+## Binaries Generation
+
+### Bootloader Binaries
+
+Base Bootloader binaries: `bootloader.bin` (ESP32 <v3.0) and `bootloader_unsigned_v2.bin` (ESP32 >=3.0) build with the configuration `CONFIG_SECURE_BOOT_BUILD_SIGNED_BINARIES=y` enabled.
+
+#### Secure Boot V1
+
+`bootloader_digested.bin`
+
+```
+espsecure digest-secure-bootloader -k 256bit_key.bin -o bootloader_digested.bin --iv 256bit_iv.bin bootloader.bin
+```
+
+`bootloader_signed.bin`
+
+```
+espsecure sign-data -v 1 -k ecdsa256_secure_boot_signing_key.pem -o bootloader_signed.bin bootloader.bin
+```
+
+#### Secure Boot V2
+
+`bootloader_signed_v2_{scheme}.bin`
+
+```
+espsecure sign-data -v 2 -k {scheme}_secure_boot_signing_key.pem -o bootloader_signed_v2_{scheme}.bin bootloader_unsigned_v2.bin
+```
+
+
+`bootloader_multi_signed_v2.bin`
+
+```
+espsecure sign-data -v 2 -a -k rsa_secure_boot_signing_key.pem rsa_secure_boot_signing_key2.pem rsa_secure_boot_signing_key3.pem -o bootloader_multi_signed_v2.bin bootloader_unsigned_v2.bin
+```
+
+`pre_calculated_bootloader_signature_{scheme}.bin`
+
+Generate signatures using the key `{scheme}_secure_boot_signing_key.pem` and `openssl`: [Secure-Boot V2 Documentation](https://docs.espressif.com/projects/esp-idf/en/latest/security/secure-boot-v2.html#generating-and-verifying-signatures-using-openssl)
+
+### Flash Encryption
+
+`bootloader-encrypted.bin`
+
+```
+espsecure encrypt-flash-data -k 256bit_key.bin -a 0x1000 --flash-crypt-conf 0xF -o bootloader-encrypted.bin bootloader.bin
+```
+
+`bootloader-encrypted-conf{conf:x}.bin`
+
+```
+espsecure encrypt-flash-data -k 256bit_key.bin -a 0x1000 --flash-crypt-conf {conf} -o bootloader-encrypted-conf{conf:x}.bin bootloader.bin
+
+where, conf = [0x0, 0x3, 0x9, 0xC]
+```
+
+`bootloader-encrypted-aes-xts.bin`
+
+```
+espsecure encrypt-flash-data -k 256bit_key.bin -a 0x1000 -x -o bootloader-encrypted-aes-xts.bin bootloader.bin
+```
+
+## Application Binaries
+
+Base Application binaries: `hello-world-signed.bin`
+
+### Flash Encryption
+
+`hello-world-signed-encrypted.bin`
+
+```
+espsecure encrypt-flash-data -k ef-flashencryption-key.bin -a 0x20000 --flash-crypt-conf 0xF -o hello-world-signed-encrypted.bin hello-world-signed.bin
+```
+
+`hello-world-signed-encrypted-aes-xts.bin`
+
+```
+espsecure encrypt-flash-data -k ef-flashencryption-key.bin -a 0x20000 -x -o hello-world-signed-encrypted-aes-xts.bin hello-world-signed.bin
+```
+
+`hello-world-signed-encrypted-aes-xts-256.bin`
+
+```
+espsecure encrypt-flash-data -k 512bit_key.bin -a 0x10000 -x -o hello-world-signed-encrypted-aes-xts-256.bin hello-world-signed.bin
+```