qax-os/excelize · error

ErrUnknownEncryptMechanism

ErrUnknownEncryptMechanism

Error message

unknown encryption mechanism

What it means

ErrUnknownEncryptMechanism indicates that the workbook's encrypted package did not contain enough bytes to read an encryption mechanism specifier (fewer than 4 bytes). The library throws it from encryptionMechanism when parsing the EncryptionInfo stream of an encrypted XLSX file and the header is too short to identify the mechanism.

Source

Thrown at errors.go:179

	ErrSparklineLocation = errors.New("parameter 'Location' is required")
	// ErrSparklineRange defined the error message on missing sparkline Range
	// parameters
	ErrSparklineRange = errors.New("parameter 'Range' is required")
	// ErrSparklineStyle defined the error message on receive the invalid
	// sparkline Style parameters.
	ErrSparklineStyle = errors.New("parameter 'Style' value must be an integer from 0 to 35")
	// ErrSparklineType defined the error message on receive the invalid
	// sparkline Type parameters.
	ErrSparklineType = errors.New("parameter 'Type' value must be one of 'line', 'column' or 'win_loss'")
	// ErrTotalSheetHyperlinks defined the error message on hyperlinks count
	// overflow.
	ErrTotalSheetHyperlinks = errors.New("over maximum limit hyperlinks in a worksheet")
	// ErrTransparency defined the error message for receiving a transparency
	// value exceeds limit.
	ErrTransparency = errors.New("transparency value must be an integer from 0 to 100")
	// ErrUnknownEncryptMechanism defined the error message on unsupported
	// encryption mechanism.
	ErrUnknownEncryptMechanism = errors.New("unknown encryption mechanism")
	// ErrUnprotectSheet defined the error message on worksheet has set no
	// protection.
	ErrUnprotectSheet = errors.New("worksheet has set no protect")
	// ErrUnprotectSheetPassword defined the error message on remove sheet
	// protection with password verification failed.
	ErrUnprotectSheetPassword = errors.New("worksheet protect password not match")
	// ErrUnprotectWorkbook defined the error message on workbook has set no
	// protection.
	ErrUnprotectWorkbook = errors.New("workbook has set no protect")
	// ErrUnprotectWorkbookPassword defined the error message on remove workbook
	// protection with password verification failed.
	ErrUnprotectWorkbookPassword = errors.New("workbook protect password not match")
	// ErrUnsupportedEncryptMechanism defined the error message on unsupported
	// encryption mechanism.
	ErrUnsupportedEncryptMechanism = errors.New("unsupported encryption mechanism")
	// ErrUnsupportedHashAlgorithm defined the error message on unsupported
	// hash algorithm.
	ErrUnsupportedHashAlgorithm = errors.New("unsupported hash algorithm")

View on GitHub (pinned to f2483381fb)

Solutions

1. Verify the file is a valid, complete encrypted XLSX (OLE compound file with non-empty EncryptionInfo stream)
2. Re-export or re-download the workbook to repair truncation/corruption
3. If encrypting, ensure the password/options passed to SaveAs/Encrypt are valid so a proper EncryptionInfo is written

Example fix

// before
f, err := OpenFile("corrupted-truncated.xlsx")
// after
info, _ := os.Stat("file.xlsx")
if info.Size() < 1024 { return errors.New("file looks truncated") }
f, err := OpenFile("file.xlsx")

info, err := os.Stat(path)
if err != nil || info.Size() < 1024 { /* likely truncated; skip */ }
// also check it is an OLE compound file (starts with D0 CF 11 E0) before opening encrypted files

func looksEncrypted(data []byte) bool {
	return len(data) > 8 && bytes.Equal(data[:8], []byte{0xD0, 0xCF, 0x11, 0xE0, 0xA1, 0xB1, 0x1A, 0xE1})
}

f, err := excelize.OpenFile(path)
if errors.Is(err, excelize.ErrUnknownEncryptMechanism) {
	return fmt.Errorf("%s is not a valid encrypted workbook", path)
}

When it happens

Trigger: Calling OpenReader/OpenFile (or Decrypt) on a file whose EncryptionInfo stream is empty or shorter than 4 bytes; in tests this is triggered by encryptionMechanism([]byte{}).

Common situations: Opening a corrupted or truncated encrypted workbook; passing a non-OLE compound file or an empty EncryptionInfo stream; a file produced by a broken encryption tool.

Related errors

• ErrWorkbookFileFormat
• ErrPasswordLengthInvalid
• ErrUnsupportedEncryptMechanism
• fill type value must be one of 'gradient' or 'pattern'
• fill color value must be an array of two colors for 'gradien

AI-assisted analysis of qax-os/excelize@f2483381fb (2026-09-02). Data as JSON: /api/errors/c642a3e2d95a2133. Report an issue: GitHub.