A cryptologic system comprising: memory; a blockchain (100, 150) stored within the memory, the blockchain (100, 150) comprising: a first block (B2, 106, 202) comprising original data; and a second block comprising: a first integrity output (IC,..., IC(Bn-1)) computed using the original data as an input; and a second integrity output (IC,..., IC(Bn-1) computed using the original data as an input; characterized in that the system comprises circuitry configured to: determine, using a first key secret, collision data including altered data, the collision data being coding-consistent with the first integrity output (IC,..., IC(Bn-1)) and coding-inconsistent with the second integrity output (IC,..., IC(Bn-1)); perform a tamper-evident rewrite of the blockchain (100, 150) by replacing the original data with the collision data; and generate a rewrite artifact in the blockchain (100, 150) by rewriting the first block (B2, 106, 202) with the altered data being different than the original data, the altered data coding-consistent with the first integrity output (IC,..., IC(Bn-1)) but coding-inconsistent with the second integrity output (IC,..., IC(Bn-1)). memory; a blockchain (100, 150) stored within the memory, the blockchain (100, 150) comprising: a first block (B2, 106, 202) comprising original data; and a second block comprising: a first integrity output (IC,..., IC(Bn-1)) computed using the original data as an input; and a second integrity output (IC,..., IC(Bn-1) computed using the original data as an input; characterized in that the system comprises a first block (B2, 106, 202) comprising original data; and a second block comprising: a first integrity output (IC,..., IC(Bn-1)) computed using the original data as an input; and a second integrity output (IC,..., IC(Bn-1) computed using the original data as an input; a first integrity output (IC,..., IC(Bn-1)) computed using the original data as an input; and a second integrity output (IC,..., IC(Bn-1) computed using the original data as an input; characterized in that the system comprises circuitry configured to: determine, using a first key secret, collision data including altered data, the collision data being coding-consistent with the first integrity output (IC,..., IC(Bn-1)) and coding-inconsistent with the second integrity output (IC,..., IC(Bn-1)); perform a tamper-evident rewrite of the blockchain (100, 150) by replacing the original data with the collision data; and generate a rewrite artifact in the blockchain (100, 150) by rewriting the first block (B2, 106, 202) with the altered data being different than the original data, the altered data coding-consistent with the first integrity output (IC,..., IC(Bn-1)) but coding-inconsistent with the second integrity output (IC,..., IC(Bn-1)). determine, using a first key secret, collision data including altered data, the collision data being coding-consistent with the first integrity output (IC,..., IC(Bn-1)) and coding-inconsistent with the second integrity output (IC,..., IC(Bn-1)); perform a tamper-evident rewrite of the blockchain (100, 150) by replacing the original data with the collision data; and generate a rewrite artifact in the blockchain (100, 150) by rewriting the first block (B2, 106, 202) with the altered data being different than the original data, the altered data coding-consistent with the first integrity output (IC,..., IC(Bn-1)) but coding-inconsistent with the second integrity output (IC,..., IC(Bn-1)).