Adobe Acrobat DC — Fixing up Form Fields?

A Chilkat customer signed a PDF using the Chilkat API. There were no errors, and the output PDF seemed to be signed. Using the Chilkat API to verify the signed PDF was also successful. Chilkat could see the signature and validated it successfully. However, the signature in the signed PDF could not be seen in Adobe Acrobat DC. When the […]

XmlDSig Error: Did not find same-document Reference Id

If signing XML fails with the following message in the LastErrorText: … Doing first SAX parse… checkAllReferencesFound: passNumber: 1 reference: Did not find same-document Reference Id referenceId: id-1234567890 –reference –checkAllReferencesFound … It means there was no XML element in the XML you were trying to sign that has an Id attribute with the given value. For example, your source code […]

Office365 – 451 4.7.0 Temporary server error. Please try again later. PRX5

A Chilkat user is getting this error response from He successfully got his OAuth2 access token, but then when trying to send the email, the Office365 server responded with this error indicating a temporary problem: “451 4.7.0 Temporary server error. Please try again later. PRX5 …” This is not an error caused because of the Chilkat implementation. Some temporary […]

How to Upload a .zip to Firebase Storage

Many developers would like to interact with Firebase from programming languages or operating systems that are not directly supported by Google. For example, looking at the documentation here:, we can see how to interact with Firebase storage from iOS+, Android, C++, etc. using Google’s SDK. Unless we know the actual raw HTTP requests and responses, we can’t implement from […]

Smart Card Vendors: Please document ATR’s and Driver DLLs

Chilkat auto-recognizes HSM’s (smart cards and USB tokens) by the ATR. A Smart Card Answer to Reset (ATR) is a special sequence of bytes sent by a smart card when it is powered on or reset. It serves as the initial communication between the card and the card reader or terminal. The ATR contains information about the card’s characteristics, including […]

SSH authentication using X.509 certificates

Question: I am unable to determine from the documentation if the Chilkat library supports SSH authentication using X.509 certificates.   In our application, we need to establish secure SSH connections to remote servers, and we prefer to use X.509 certificates for authentication instead of traditional username/password or key-based authentication methods. Could you please clarify if the Chilkat SSH/SFTP API’s support X.509 […]

Chilkat Updated to Support AKiS Smart Cards

AKiS is a smart card operating system which can be used in personal identification, digital sign, health care system, smart logon, secure email, etc. It is developed within The National Research Institute Of Electronics And Cryptology (UEKAE), a subsidiary of The Scientific & Technological Research Council of Turkey (TUBITAK). There was a problem relating to e-signature tokens using AKIS cards. […]

Malaysia EInvoice

Questions: We are struggling to fulfill the EInvoice implementation mandate from Malaysian government, which is on 1st August 2024 (3 months from now). We wish to implement a direct integration from the company system to the government system through API (EInvoice submission and retrieval). After studying the guidance from the government on Digital Signature at … Our […]

Office365 SMTP AUTH XOAUTH2 Fails with “535 5.7.3 Authentication unsuccessful”

If you successfully minted an OAuth2 access token for your Azure Entra Id App, but then it fails when attempting to use it in the SMTP protocol for sending email with the error: AUTH XOAUTH2 user=xxx auth=Bearer ********************** 535 5.7.3 Authentication unsuccessful [ 2024-04-16T12:11:26.548Z 08DC9999186DF999] Check your Entra Id App Registration to make sure you have the following App Permissions:

How to Troubleshoot Office365 IMAP AUTHENTICATE XOAUTH2 Failed

Question: We have an issue reading mail and we see the below error message in log Login: DllDate: Oct 27 2023 ChilkatVersion: UnlockPrefix: *** UnlockStatus: 2 Architecture: Little Endian; 32-bit Language: *** VerboseLogging: 0 imapServer: loginX(2219ms): login: greeting: * OK The Microsoft Exchange IMAP4 service is ready. [***] authenticateXOAuth2(2219ms): xoauth2Imap(2219ms): ConnectionType: SSL/TLS ImapCmdSent: aaab AUTHENTICATE XOAUTH2 ImapCmdResp: […]