Function computeUValueRc4_128

computeUValueRc4_128(
    userPassword: ByteArray,
    oValue: ByteArray,
    permissions: number,
    id: ByteArray,
    encryptMetadata: boolean,
    revision?: number,
): Promise<ByteArray>
Computes the /U value for RC4-128 PDF encryption. The /U value is used to verify the user password.
Parameters
- userPassword: ByteArray
  The user password.
- oValue: ByteArray
  The /O value.
- permissions: number
  The /P value (permissions flags).
- id: ByteArray
  The first element of the /ID array.
- encryptMetadata: boolean
  Whether to encrypt metadata.
- Optionalrevision: number
  The encryption revision number.
Returns Promise<ByteArray>
A promise that resolves to the 32-byte /U value.
Example
```
const U = await computeUValueRc4_128(userPassword, O, permissions, fileId, true)
```
- Defined in packages/pdf-lite/src/crypto/key-gen/key-gen-rc4-128.ts:152