These functions are used to create and verify checksums. krb5_create_checksum creates a checksum of the specified data, and puts it in result. If crypto is NULL, usage_or_type specifies the checksum type to use; it must not be keyed. Otherwise crypto is an encryption context created by krb5_crypto_init, and usage_or_type specifies a key-usage.
krb5_verify_checksum verifies the checksum, against the provided data.
krb5_checksum_is_collision_proof returns true is the specified checksum is collision proof (that its very unlikely that two strings has the same hash value, and that its hard to find two strings that has the same hash). Examples of collision proof checksums are MD5, and SHA1, while CRC32 is not.
krb5_checksum_is_keyed returns true if the specified checksum type is keyed (that the hash value is a function of both the data, and a separate key). Examples of keyed hash algorithms are HMAC-SHA1-DES3, and RSA-MD5-DES. The "plain" hash functions MD5, and SHA1 are not keyed.