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AbsoluteTimestamp

.NET library for creating and verifying RFC 3161 timestamps. Based on Bouncy Castle. Available on NuGet.

Basic usage

Creating a timestamp

TimestampCreator creator = new TimestampCreator();
TimestampObject timestamp = creator
    .SetTsaPrimaryUrl("http://example.com/tsa")
    .SetDataForTimestamping("Example.pdf")
    .CreateTimestamp();

Verifying a timestamp

TimestampVerifier verifier = new TimestampVerifier();
TimestampObject verifiedTimestamp = verifier
    .SetTimestampedData("Example.pdf")
    .SetTimestamp(timestamp.Timestamp)
    .Verify();

API

Items highlighted in bold are mandatory. For further info see ITimestampCreator and ITimestampVerifier interfaces.

Creating a timestamp

Inputs

  • Primary TSA url - (string)
  • Hash algorithm - (HashAlgorithm enum value)
  • Data to be timestamped
    • File - (byte[], stream, string)
    • List of files - (byte[][], stream[], string[])
    • Message digest(s) - (byte[], byte[][])
  • Output format - (OutputFormat enum value)
  • Secondary TSA url - (string)
  • Primary and secondary TSA credentials - (string)
  • TSA connection timeout - (int)
  • Minimum certificate validity period - (int)

Outputs

  • Timestamp
    • TSR format
    • ASIC-S format
  • Additional info (generated time, hash algorithm, signer info, ...)

Verifying a timestamp

Inputs

  • Timestamp - (string, byte[], stream)
  • Hash algorithm - (HashAlgorithm enum value)
  • Timestamped data
    • File - (byte[], stream, string)
    • List of files - (byte[][], stream[], string[])
    • Message digest(s) - (byte[], byte[][])
  • Minimum certificate validity period - (int)

Outputs

  • Timestamp
    • TSR format
    • ASIC-S format
  • Additional info (generated time, hash algorithm, signer info, ...)

Configuration file

Utils.LoadConfigurationFile("path/to/configuration/file.txt");

Several data, required for working with timestamps, can be provided through configuration file. Static data that doesn’t change, such as credentials to access TSA, can be retrieved from this file. This way the user doesn't have to specify these settings every time he wants to create or verify a timestamp. The configuration file is a simple text file. Each row contains exactly one key-value pair of settings separated with equals sign (example: hash.algorithm=sha1).

Configuration name Description Value
tsa.primary.url Url address of primary TSA
tsa.primary.username Username for accessing protected TSA
tsa.primary.password Password for accessing protected TSA
tsa.secondary.url Url address of secondary TSA
tsa.secondary.username Username for accessing protected TSA
tsa.secondary.password Password for accessing protected TSA
tsa.timeout TSA connection timeout limit (milliseconds)
hash.algorithm Hash algorithm used to create message digest MD5/SHA1/SHA256/SHA512
timestamp.output Specifies format of timestamp that is returned TSR/ASICS
certificate.minimum.validity Minimum time period when signing certificate has to be valid (days)