A method for assessing entropy in a cryptography system, the method comprising: obtaining, by a hardware data processing apparatus, a plurality of sample values produced by an entropy source system; determining, by the hardware data processing apparatus, a typicality grading for each of a preselected plurality of probability distributions, the typicality gradings providing a comparison among the plurality of probability distributions, the typicality grading for each individual probability distribution being determined based on the respective probabilities of selecting the plurality of sample values from that individual probability distribution, wherein the typicality grading for each individual probability distribution is determined based on a cumulative probability with respect to that individual probability distribution, and determining the typicality grading for each individual probability distribution comprises calculating ∑ y: P p y ≤ P p x P p y, where P p ( x) represents a probability of a sample value x of the plurality of sample values according to the individual probability distribution p, and y: P p ( y) ≤ P p ( x) represents values that are at most as probable as the sample value x; selecting, by the hardware data processing apparatus, a subset of the plurality of probability distributions based on the typicality gradings; calculating, by the hardware data processing apparatus, an entropy of the entropy source system based on the subset of the plurality of probability distributions, wherein the calculated entropy is used to determine a security risk of the entropy source system; determining, by the hardware data processing apparatus, whether the entropy source system has adequate entropy to achieve a specified security level in the cryptography system; modifying, by the hardware data processing apparatus, the entropy source system based on a determination that the entropy source system has inadequate entropy; encrypting, by the hardware data processing apparatus, a message using the modified entropy source system; and transmitting, by the hardware data processing apparatus, the encrypted message. obtaining, by a hardware data processing apparatus, a plurality of sample values produced by an entropy source system; determining, by the hardware data processing apparatus, a typicality grading for each of a preselected plurality of probability distributions, the typicality gradings providing a comparison among the plurality of probability distributions, the typicality grading for each individual probability distribution being determined based on the respective probabilities of selecting the plurality of sample values from that individual probability distribution, wherein the typicality grading for each individual probability distribution is determined based on a cumulative probability with respect to that individual probability distribution, and determining the typicality grading for each individual probability distribution comprises calculating ∑ y: P p y ≤ P p x P p y, where P p ( x) represents a probability of a sample value x of the plurality of sample values according to the individual probability distribution p, and y: P p ( y) ≤ P p ( x) represents values that are at most as probable as the sample value x; selecting, by the hardware data processing apparatus, a subset of the plurality of probability distributions based on the typicality gradings; calculating, by the hardware data processing apparatus, an entropy of the entropy source system based on the subset of the plurality of probability distributions, wherein the calculated entropy is used to determine a security risk of the entropy source system; determining, by the hardware data processing apparatus, whether the entropy source system has adequate entropy to achieve a specified security level in the cryptography system; modifying, by the hardware data processing apparatus, the entropy source system based on a determination that the entropy source system has inadequate entropy; encrypting, by the hardware data processing apparatus, a message using the modified entropy source system; and transmitting, by the hardware data processing apparatus, the encrypted message.