A method to enhance blockchains, comprising: additional fields (205, 206) in a block (200,201) where additional values (421, 422) provided by a back step generator are inserted before the block is hashed which are used to build a cryptographic backward chain from the block to its previous block and from this previous block to its previous block and so on until a first genesis block is reached providing cryptographic security to detect manipulated chains, wherein the additional values (421, 422) comprise a back step value and a seal; a back step generator as secured logic (300, 400) providing the required values (421, 422); a non-secret cryptographic one-way function (317, 318) for building the values (421, 422) embedded in the back step generator and logically applied between adjacent blocks, such that the values of the previous block can be easily calculated from the current block in the chain, while calculating the values of a future block is cryptographically hard; a secured storage (303, 304) that holds initial secrets for a generation of the back step value and a back step seal value; a logic as part of the back step generator that calculates the seal from the hash value of the previous block and the current back step seal value in such a way that a backward calculation to the back step seal value is cryptographically hard; a logic inside the back step generator that pre-calculates back step and back step seal values by repeated application of the one-way function (317, 318) to the initial secrets; a cache logic inside the back step generator that provides back step and back step seal values (418, 422) in time for a calculation of the block; a controller logic and a checkpoint address logic that stores such pre-calculated values periodically after a defined number of steps in a secured non-volatile storage as checkpoint values and to fetch them back whenever the cache needs to be refilled; a cache controller that manages alternate refill and depletion of two-cache storage blocks (406, 407) such that back step and back step seal values are immediately available whenever the next block needs to be hashed; a logic that delivers the backstep seal value for a defined step of the chain to authorized people or institution for external verification of the correctness of the chain; a non-volatile secure storage inside the back step generator that stores secrets used to verify the authenticity of a seal value delivery request; a non-volatile secure storage that stores protection secrets used to protect the backstep seal value at delivery time; a seal protection logic that protects the backstep seal value against unauthorized use. additional fields (205, 206) in a block (200,201) where additional values (421, 422) provided by a back step generator are inserted before the block is hashed which are used to build a cryptographic backward chain from the block to its previous block and from this previous block to its previous block and so on until a first genesis block is reached providing cryptographic security to detect manipulated chains, wherein the additional values (421, 422) comprise a back step value and a seal; a back step generator as secured logic (300, 400) providing the required values (421, 422); a non-secret cryptographic one-way function (317, 318) for building the values (421, 422) embedded in the back step generator and logically applied between adjacent blocks, such that the values of the previous block can be easily calculated from the current block in the chain, while calculating the values of a future block is cryptographically hard; a secured storage (303, 304) that holds initial secrets for a generation of the back step value and a back step seal value; a logic as part of the back step generator that calculates the seal from the hash value of the previous block and the current back step seal value in such a way that a backward calculation to the back step seal value is cryptographically hard; a logic inside the back step generator that pre-calculates back step and back step seal values by repeated application of the one-way function (317, 318) to the initial secrets; a cache logic inside the back step generator that provides back step and back step seal values (418, 422) in time for a calculation of the block; a controller logic and a checkpoint address logic that stores such pre-calculated values periodically after a defined number of steps in a secured non-volatile storage as checkpoint values and to fetch them back whenever the cache needs to be refilled; a cache controller that manages alternate refill and depletion of two-cache storage blocks (406, 407) such that back step and back step seal values are immediately available whenever the next block needs to be hashed; a logic that delivers the backstep seal value for a defined step of the chain to authorized people or institution for external verification of the correctness of the chain; a non-volatile secure storage inside the back step generator that stores secrets used to verify the authenticity of a seal value delivery request; a non-volatile secure storage that stores protection secrets used to protect the backstep seal value at delivery time; a seal protection logic that protects the backstep seal value against unauthorized use.