We define portable C to be 1990 ISO standard compliant C (ISO/IEC 9899:1990, the amendment ISO/IEC 9899 AM1, and the two technical corrigenda ISO/IEC 9899 TCOR1 and TCOR2; hereafter called C90) with following relaxations and/or additional requirements:

• Two's complement representation of signed integers may be assumed.
• Define and use minimum-width integer types and macro's to obtain exact-width results from these minimum-width integers. Use of the long long type (or equivalents such as the __int64 type), if available, is allowed.
• Endianness conversion (if required) should only be performed on input/output data.
• Define and use macro's for operations that are not available in standard C90 and/or may be overridden by architecture-specific operations for optimization reasons.
• Comments should use the /* ... */ syntax, not the C++-like // syntax.

• ecrypt-config.h,
• ecrypt-machine.h,
• ecrypt-portable.h,

• Definitions of  minimum-width integer types and macro's to obtain exact-width results from these minimum-width integers.
• Robust macro's for endianness conversion.
• An example definition of a macro for an operation that is not available in standard C90 and may be overridden by an architecture-specific operation for optimization reasons (the rotate operation).