An arbitrary precision integer math library (also known as bignums) implemented in pure Tcl under the BSD license can be found at http://wiki.hping.org/108. Hopefully it will be available in Tcllib in short time. In this page you can also find usage examples about RSA and Diffie-Hellman Key Agreement Protocol.

See also math::bignum

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Note that Tcl 8.5 includes extensive bignum support.

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