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func extractKeyFromASN1(_ keyBytes: Data) -> Data? {
guard keyBytes.count > 0 else { return nil }
var index = 22 // ASN.1 struct must have 0x04 at byte 22
guard keyBytes[index] == 0x04 else { return nil }
index += 1
var keyLength = Int(keyBytes[index])
index += 1
let isLengthCodedInMultiBytes = keyLength & 0x80 // higth length bit
if isLengthCodedInMultiBytes == 0 {
keyLength = keyLength & 0x7f // length is coded in 7 low bits
} else {
var byteCount = Int(keyLength & 0x7f) // otherwise, number of bytes is coded in 7 low bits
guard byteCount + index <= keyBytes.count else { return nil }
keyLength = 0
while (byteCount > 0) {
keyLength = (keyLength * 256) + Int(keyBytes[index])
index += 1
byteCount -= 1
}
}
return keyBytes[index..<index+keyLength]
}
OlivierPi
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Hello, function to extract the key data
guard keyBytes.count > 0 else { return nil }
var index = 22 // ASN.1 struct must have 0x04 at byte 22
guard keyBytes[index] == 0x04 else { return nil }
index += 1
var keyLength = Int(keyBytes[index])
index += 1
let isLengthCodedInMultiBytes = keyLength & 0x80 // higth length bit
if isLengthCodedInMultiBytes == 0 {
keyLength = keyLength & 0x7f // length is coded in 7 low bits
} else {
var byteCount = Int(keyLength & 0x7f) // otherwise, number of bytes is coded in 7 low bits
guard byteCount + index <= keyBytes.count else { return nil }
keyLength = 0
while (byteCount > 0) {
keyLength = (keyLength * 256) + Int(keyBytes[index])
index += 1
byteCount -= 1
}
}
return keyBytes[index..<index+keyLength]
}