Q: I want to add timestamps when adding digital signatures to PDF documents in PDF Studio. Do you have a list of timestamp servers available?
A: We added support for SHA512 algorithm for communication with timestamp servers in version 2020. This FreeTSA – Guide recommends using SHA-512. SHA-512 is part of SHA-2 (read more on md5hashing.net).
Below is the list of timestamp servers that we found working:
| Timestamp Server | SHA512 PDF Studio 2021+ |
|---|---|
| https://freetsa.org/tsr |  SHA512 |
| http://tsatest1.digistamp.com/tsa (requires authentication) | SHA512 |
| http://time.certum.pl | SHA512 |
| http://timestamp.digicert.com | SHA512 |
| http://zeitstempel.dfn.de | SHA512 (Must increase padding length to 8000) |
| http://timestamp.apple.com/ts01 | SHA512 |
| http://timestamp.entrust.net/TSS/RFC3161sha2TS | SHA512 |
| http://tsa.cesnet.cz:3161/tsa | SHA512 |
| https://tsa.cesnet.cz:3162/tsa | SHA512 |
| http://tsa.cesnet.cz:5816/tsa | SHA512 |
| https://tsa.cesnet.cz:5817/tsa | SHA512 |
